Transmission driver, electronic device, and control method of electronic device

ABSTRACT

A transmission driver receives an input signal, a first voltage, and a second voltage higher than the first voltage, and transmits a transmission signal according to the input signal, the transmission driver includes an output terminal that outputs the transmission signal and circuitry that is coupled to the output terminal and that operates in a first mode of transmitting the transmission signal with a first voltage range that ranges from the first voltage to the second voltage, and a second mode of transmitting the transmission signal with a second voltage range that ranges from the first voltage to a third voltage higher than the second voltage.

BACKGROUND Technical Field

The present disclosure relates to a transmission driver, andparticularly, to a transmission driver, an electronic device providedwith the transmission driver, and a control method of the electronicdevice.

Description of the Related Art

A transmission driver that transmits a transmission signal according toan input signal and an electronic device, such as a tablet terminal anda stylus, provided with the transmission driver have hitherto beenknown.

In relation to this, a tablet terminal is disclosed in Japanese PatentLaid-Open No. 2019-091442, the tablet terminal including a plurality ofsensor electrodes, output signal lines each provided for each sensorelectrode and connected to the sensor electrode, switches each providedfor each output signal line, one end of the switch being connected tothe output signal line, another end of the switch being connected to ashort-circuit line, and a control signal line for controlling eachswitch. In the technique disclosed in Japanese Patent Laid-Open No.2019-091442, the output signal line with the voltage in a high level andthe output signal line with the voltage in a low level areshort-circuited, and the charge is shared between the output signallines to reduce power consumption.

The technique can be applied to electronic devices other than the tabletterminal, such as a stylus used together with the tablet terminal.However, depending on the type of stylus, in some cases, thetransmission driver that outputs signals to the output signal lines maybe a single unit, or a plurality of transmission drivers may be arrangedat separate positions. Hence, there is a problem that the techniquecannot be applied. In addition, the voltage difference between the highlevel and the low level of the signal may need to be large in anelectromagnetic-coupling stylus.

BRIEF SUMMARY

The present disclosure has been made in view of the problems, and anobject of the present disclosure is to provide a transmission driverthat can independently reduce power consumption, an electronic deviceprovided with the transmission driver, and a control method of theelectronic device.

To solve the problems, a first aspect of the present disclosure providesa transmission driver that receives an input signal, a first voltage,and a second voltage higher than the first voltage and that transmits atransmission signal according to the input signal, the transmissiondriver includes an output terminal which, in operation, outputs thetransmission signal; and circuitry coupled to the output terminal,wherein the circuitry, in operation, operates in: a first mode oftransmitting the transmission signal with a first voltage range thatranges from the first voltage to the second voltage, and a second modeof transmitting the transmission signal with a second voltage rangesthat ranges from the first voltage to third voltage higher than thesecond voltage.

A second aspect of the present disclosure provides the transmissiondriver further including a booster circuit which, in operation, suppliesthe third voltage.

A third aspect of the present disclosure provides the transmissiondriver further including an output control circuit which, in operation,receives the first voltage and one of the second voltage and the thirdvoltage and outputs the transmission signal from the output terminal,and a short-circuit control element that controls supply of the secondvoltage to the output control circuit.

A fourth aspect of the aspect of the present disclosure provides thetransmission driver in which the booster circuit includes a capacitiveelement.

A fifth aspect of the present disclosure provides the transmissiondriver in which, in the first mode, the second voltage is supplied tothe output control circuit through the short-circuit control element,and in the second mode, the short-circuit control element cuts off thesupply of the second voltage to the output control circuit, and thebooster circuit supplies the third voltage to the output controlcircuit.

A sixth aspect of the present disclosure provides the transmissiondriver in which the output control circuit includes a positive powersupply terminal and a negative power supply terminal, the first voltageis supplied to the negative power supply terminal, the second voltage issupplied to one end of the short-circuit control element, and anotherend of the short-circuit control element and one end of the capacitiveelement are connected to the positive power supply terminal.

A aspect of the seventh present disclosure provides the transmissiondriver further including a signal generation circuit which, inoperation, generates a first signal and a second signal according to theinput signal, in which the output control circuit sets, as thetransmission signal, a first supplied voltage that is supplied to thepositive power supply terminal or a second supplied voltage that issupplied to the negative power supply terminal, according to the firstsignal, and outputs the transmission signal, and the second signal isinput to a second end of the capacitive element.

An eighth aspect of the present disclosure provides the transmissiondriver further including a control circuit which, in operation, controlsthe short-circuit control element to short-circuit the short-circuitcontrol element when a first signal voltage of the first signal is thefirst voltage and to open the short-circuit control element when thefirst signal voltage of the first signal is a fourth voltage higher thanthe first voltage, in which the signal generation circuit generates thefirst signal such that the first signal voltage of the first signal isshifted from the first voltage to the fourth voltage at a first timingcorresponding to a rise of the input signal and the first signal voltageof the first signal is shifted from the fourth voltage to the firstvoltage at a fourth timing at which a predetermined time period haspassed from a third timing corresponding to a fall of the input signal,and the signal generation circuit generates the second signal such thatthe a second signal voltage of the second signal is shifted from thefirst voltage to fifth voltage higher than the first voltage at a secondtiming at which a predetermined time period has passed from the firsttiming and the second signal voltage of the second signal is shiftedfrom the fifth voltage to the first voltage at the third timing.

A ninth aspect of the present disclosure provides the transmissiondriver in which a time period from the first timing to the second timingis equal to or smaller than half a time period from the first timing tothe third timing, and a time period from the third timing to the fourthtiming is equal to or smaller than half a time period from the secondtiming to the fourth timing.

A tenth aspect of the present disclosure provides the transmissiondriver in which the fourth voltage and the fifth voltage are equal tothe second voltage.

An eleventh aspect of the present disclosure provides the transmissiondriver in which capacitance of the capacitive element is equal to orgreater than ten times parasitic capacitance connected to the outputterminal.

A twelfth aspect of the present disclosure provides the transmissiondriver such that the circuitry, in operation, operates in a third modeof transmitting the transmission signal with a third voltage range thatranges from the first voltage to sixth voltage higher than the thirdvoltage.

A thirteenth aspect of the present disclosure provides the transmissiondriver further including a first booster circuit which, in operation,supplies the third voltage or the sixth voltage.

A fourteenth aspect of the present disclosure provides the transmissiondriver further including a second booster circuit which, in operation,supplies, to the first booster circuit, seventh voltage higher than thefirst voltage by a difference between the third voltage and the secondvoltage or an eighth voltage higher than the seventh voltage by adifference between the sixth voltage and the second voltage.

A fifteenth aspect of the present disclosure provides the transmissiondriver in which the first booster circuit includes a first capacitiveelement that supplies the third voltage or the sixth voltage from oneend of the first capacitive element, the second booster circuit includesa second capacitive element that supplies the seventh voltage or theeighth voltage from one end of the second capacitive element to thefirst booster circuit, and a first capacitance of the first capacitiveelement is 0.6 times a total of the first capacitance of the firstcapacitive element and a second capacitance of the second capacitiveelement.

A sixteenth aspect of the present disclosure provides the transmissiondriver such that the circuitry, in operation, operates in a fourth modeof transmitting the transmission signal with a fourth voltage range thatranges from the first voltage to a ninth voltage that is voltage betweenthe first voltage and the second voltage; and a fifth mode oftransmitting the transmission signal with a fifth voltage range thatranges from the first voltage to a tenth voltage that is voltage betweenthe second voltage and the third voltage.

A seventeenth aspect of the present disclosure provides the transmissiondriver further including a third booster circuit which, in operation,supplies the ninth voltage, the tenth voltage, or the third voltage.

An eighteenth aspect of the present disclosure provides the transmissiondriver in which the third booster circuit divides the first voltage andthe second voltage to generate the ninth voltage and boosts the ninthvoltage that is generated by an amount of the second voltage to generatethe tenth voltage.

A nineteenth aspect of the present disclosure provides an electronicdevice including first electrodes that transmit and receive signals, anda transmission driver that receives an input signal, a first voltage,and a second voltage higher than the first voltage, generates atransmission signal according to the input signal, and transmits thetransmission signal to corresponding one of the electrodes, in which thetransmission driver, in operation, operates in a first mode oftransmitting the transmission signal with a first voltage ranges thatranges from the first voltage to the second voltage, and a second modeof transmitting the transmission signal with a second voltage rangesthat ranges from the first voltage to third voltage higher than thesecond voltage.

A twentieth aspect of the present disclosure provides the electronicdevice in which the transmission driver is mounted on a stylus, thefirst electrodes are mounted on the stylus and transmit and receive thesignals through capacitive coupling between the first electrodes andsecond electrodes mounted on a sensor that is connected to a sensorcontroller, and the stylus side electrodes are mounted on the stylus.

A twenty-first aspect of the present disclosure provides a controlmethod of an electronic device that operates in a first mode and asecond mode, the electronic device including electrodes that transmitand receive signals, and a transmission driver that receives an inputsignal, a first voltage, and a-second voltage higher than the firstvoltage and that transmits a transmission signal to the electrodesaccording to the input signal, the control method including, in a firstmode, transmitting the transmission signal with a first voltage rangesthat ranges from the first voltage to the second voltage, and in asecond mode, transmitting the transmission signal with a second voltageranges that ranges from the first voltage to third voltage higher thanthe second voltage.

According to the present disclosure, the transmission driver canindependently reduce the power consumption.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts an example of a stylus system;

FIG. 2 depicts an example of a touch sensor mounted apparatusillustrated in FIG. 1 ;

FIG. 3 depicts an example of part of a circuit configuration of anoutput circuit and a touch sensor illustrated in FIG. 2 ;

FIG. 4 depicts an example of a stylus illustrated in FIG. 1 ;

FIG. 5 depicts an example of a transmission driver according to a firstembodiment;

FIG. 6 is a timing chart illustrating an example of a shift in voltageof each signal in the transmission driver according to the firstembodiment;

FIG. 7 is a flow chart illustrating an example of a flow of a series ofprocesses of an electronic device including the transmission driveraccording to the first embodiment;

FIG. 8 depicts an example of a transmission driver according to a secondembodiment;

FIG. 9 is a timing chart illustrating an example of a shift in voltageof each signal in the transmission driver according to the secondembodiment;

FIG. 10 is a flow chart illustrating an example of a flow of a series ofprocesses of an electronic device including the transmission driveraccording to the second embodiment;

FIG. 11 depicts an example of a transmission driver according to a thirdembodiment;

FIG. 12 is a timing chart illustrating an example of a shift in voltageof each signal in the transmission driver according to the thirdembodiment;

FIG. 13 is a flow chart illustrating an example of a flow of a series ofprocesses of an electronic device including the transmission driveraccording to the third embodiment;

FIG. 14 is a chart illustrating an example of a relation between thecapacitance of capacitive elements and the voltage of a transmissionsignal in the transmission driver according to the second embodiment;and

FIG. 15 is a graph illustrating an example of a relation between theratio of the capacitance of the capacitive elements and the voltage ofthe transmission signal in the transmission driver according to thesecond embodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure (hereinafter, referred to as“present embodiments”) will now be described with reference to theattached drawings. To facilitate the understanding of the description,the same reference signs are provided as much as possible to the sameconstituent elements and steps in the drawings, and the description willnot be repeated.

First Embodiment

A first embodiment will be described.

Circuit Configuration

FIG. 1 depicts an example of a stylus system 1 according to the presentdisclosure. The stylus system 1 is, for example, a system of an activecapacitance type. The stylus system 1 includes a touch sensor 30 placedover a display apparatus such as a liquid crystal panel, a touch sensormounted apparatus 3 including a sensor controller 10 that uses the touchsensor 30 to derive a current instruction position of the stylus 2 andthat outputs the instruction position to a control circuit 12 along withoperation state data, and a stylus 2 (active stylus) for inputting aninstruction position, operation state data, such as pen pressure, andother data to the touch sensor mounted apparatus 3. The stylus 2 and thetouch sensor mounted apparatus 3 are electronic devices and arecapacitively coupled to each other through capacitance Cpen. Thecapacitance of the capacitance Cpen is typically smaller than 10 pF.

The stylus 2 is, for example, a stylus of an active capacitive couplingtype (AES) that detects an uplink signal US transmitted from the sensorcontroller 10 at a predetermined cycle and that includes a power supply,a communication circuit, and electrodes for transmitting a downlinksignal DS in a time period instructed based on the time of the detecteduplink signal US.

The touch sensor mounted apparatus 3 is a computer owned by a user andincludes, for example, a tablet, a smartphone, or a personal computer.The touch sensor mounted apparatus 3 detects the instruction position ofthe stylus 2 and executes various types of information processingaccording to the detection result. Specifically, the touch sensormounted apparatus 3 transmits the uplink signal US to the stylus 2,detects the instruction position of the stylus 2 according to the resultof reception of the downlink signal DS from the stylus 2, and executes ageneration process of digital ink, a display process of a pointer, andthe like. The touch sensor mounted apparatus 3 includes a hostprocessor, a memory, a communication module (that are not illustrated),and the like in addition to the sensor controller 10 and the touchsensor 30.

FIG. 2 depicts an example of the touch sensor mounted apparatus 3illustrated in FIG. 1 .

The touch sensor 30 is a sensor of capacitance type including aplurality of detection electrodes arranged in a plane shape. The touchsensor 30 includes, for example, a plurality of X line electrodes(hereinafter, referred to as “linear electrodes 31”) for detecting theposition of the X-axis in the sensor coordinate system and a pluralityof Y line electrodes (hereinafter, referred to as “linear electrodes32”) for detecting the position of the Y-axis in the sensor coordinatesystem. The linear electrodes 31 and the linear electrodes 32 maycontain a transparent conductive material including indium tin oxide(ITO) or may include wire mesh sensors. Note that the touch sensor 30may be a sensor of self-capacitance type including block-like electrodesarranged in a two-dimensional grid, instead of the sensor of mutualcapacitance type.

The sensor controller 10 includes a micro controller unit (MCU) 11, thecontrol circuit 12, a transmission circuit 13, a reception circuit 14,an output circuit 15, a detection circuit 16, and selection circuits 17and 18.

The output circuit 15 is a circuit that selects one of the plurality oflinear electrodes 32 or a plurality of linear electrodes 32 adjacent toeach other, according to an instruction from the control circuit 12,amplifies an input signal transmitted from the control circuit 12 to apredetermined voltage, to set the input signal as an output signal, andoutputs the output signal to the linear electrode 32. The detectioncircuit 16 is a circuit that selects one of the plurality of linearelectrodes 31 or a plurality of linear electrodes 31 adjacent to eachother, according to an instruction from the control circuit 12.

The selection circuit 17 is, for example, a multiplexer, and is acircuit for switching whether to use the linear electrode 32 selected bythe output circuit 15, as an electrode for receiving a signal or as anelectrode for transmitting a signal. When a selection signal SELY outputfrom the control circuit 12 is in a low state “0,” the selection circuit17 connects the linear electrode 32 selected by the output circuit 15 tothe reception circuit 14 through the selection circuit 18. On the otherhand, when the selection signal SELY is in a high state “1,” theselection circuit 17 supplies the input signal input from the controlcircuit 12 through the transmission circuit 13 to the linear electrode32 selected by the output circuit 15.

The selection circuit 18 is, for example, a multiplexer, and selects asignal input through the selection circuit 17 from the linear electrode32 selected by the output circuit 15 or a signal input from the linearelectrode 31 selected by the detection circuit 16 and outputs theselected signal to the reception circuit 14. When a selection signalSELX output from the control circuit 12 is in the low state, theselection circuit 18 connects the linear electrode 32 selected by theoutput circuit 15 to the reception circuit 14. On the other hand, whenthe selection signal SELX is in the high state, the selection circuit 18connects the linear electrode 32 selected by the output circuit 15 tothe reception circuit 14 through the selection circuit 17.

The touch sensor mounted apparatus 3 includes the following four typesof modes, and the control circuit 12 controls the circuits in the sensorcontroller 10 while switching the modes in the following order. Themodes will be described in detail one by one.

A first mode is a mode of detecting the position of a finger. In themode, the control circuit 12 puts the selection signal SELY into thehigh state and puts the selection signal SELX into the low state. Thatis, the transmission signal output from the control circuit 12 throughthe transmission circuit 13 and the output circuit 15 is supplied to thelinear electrode 32 selected by the output circuit 15, and a touchdetection signal is transmitted from the touch sensor 30. The linearelectrode 31 selected by the detection circuit 16 is connected to thereception circuit 14. This configuration allows the MCU 11 to read achange in detection signal caused by contact of the finger with thesensor surface and calculate the coordinate position of the finger.

A second mode is a mode of transmitting the uplink signal US to thestylus 2. The control circuit 12 in this case puts the selection signalSELY into the high state. As a result, the transmission signal outputfrom the control circuit 12 through the transmission circuit 13 and theoutput circuit 15 is supplied to the linear electrode 32 selected by theoutput circuit 15, and the uplink signal US is transmitted from thetouch sensor 30. In this case, the output circuit 15 may select aneighborhood electrode instructed by the stylus 2 that is among thelinear electrodes 32, to transmit the uplink signal US, or the outputcircuit 15 may select all of the linear electrodes 32 at the same timeto transmit a trigger signal US_trg.

A third mode is a mode of detecting a position signal DS_pos transmittedby the stylus 2, to detect the position of the stylus 2. The controlcircuit 12 in this case puts the selection signal SELY into the lowstate, and the linear electrode 32 selected by the output circuit 15 isconnected to the reception circuit 14 through the selection circuit 17.To obtain the X-axis coordinate of the stylus 2, the control circuit 12puts the selection signal SELX into the low state and connects thelinear electrode 31 selected by the detection circuit 16 to thereception circuit 14. In this state, the MCU 11 reads, as signal levelvalues, data output from the reception circuit 14, while the detectioncircuit 16 sequentially selects, one by one, a plurality of linearelectrodes 31, such as five linear electrodes 31, around the linearelectrode 31 closest to the instruction position of the stylus 2. TheMCU 11 calculates the X-axis coordinate of the stylus 2 in reference tothe signal level distribution for the selected linear electrode 31. Toobtain the Y-axis coordinate of the stylus 2, the control circuit 12puts the selection signal SELX into the high state and connects thelinear electrode 32 selected by the output circuit 15 to the receptioncircuit 14. In this state, the MCU 11 reads, as signal level values,data output from the reception circuit 14, while the output circuit 15sequentially selects, one by one, a plurality of linear electrodes 32,such as five linear electrodes 32, around the linear electrode 32closest to the instruction position of the stylus 2. The MCU 11calculates the Y-axis coordinate of the stylus 2 in reference to thesignal level distribution for the selected linear electrode 32.

A fourth mode is a mode of receiving a data signal DS_res transmitted bythe stylus 2. Although either one of the linear electrode 31 and thelinear electrode 32 may be used to receive the data signal DS_res, thelinear electrode 31 is used to receive the data signal DS_res in thecase described here. The control circuit 12 puts the selection signalSELX into the low state to connect the linear electrode 31 selected bythe detection circuit 16 to the reception circuit 14. The controlcircuit 12 is operated such that the detection circuit 16 simultaneouslyselects a plurality of linear electrodes 31, such as three linearelectrodes 31, around the linear electrode 31 closest to the instructionposition of the stylus 2. In this state, the MCU 11 periodically readsthe output from the reception circuit 14. Note that, in the case ofusing the linear electrode 32 to receive the data signal DS_res, theselection signal SELY can be put into the low state, and the selectionsignal SELX can be put into the high state.

This completes the description of the operation of the control circuit12 in each mode. As can be understood from the description, the touchsensor mounted apparatus 3 is configured to use the same touch sensor 30to transmit and receive signals. Other components in the touch sensormounted apparatus 3 illustrated in FIG. 2 will be described below.

The MCU 11 is a microprocessor that includes a read only memory (ROM)and a random access memory (RAM) inside and that operates according to apredetermined program. The MCU 11 controls the control circuit 12 suchthat the control circuit 12 outputs the signals as described above, andexecutes a reading process for digital data output by the receptioncircuit 14.

The control circuit 12 is a logic circuit for accurately outputting eachsignal at a designated timing according to an instruction from the MCU11.

This completes the description of the configuration and the operation ofthe touch sensor mounted apparatus 3. Next, a configuration of circuitsthat function when the output circuit 15 transmits a signal to thelinear electrode 32 will be described in detail. FIG. 3 depicts anexample of part of the circuit configuration of the output circuit 15and the touch sensor 30 that are illustrated in FIG. 2 .

As illustrated in FIG. 3 , the output circuit 15 includes a driverselection circuit 151 and a plurality of transmission drivers 152A.

The driver selection circuit 151 selects some of the plurality oftransmission drivers 152A that transmit signals to the linear electrodes32 according to an instruction of the control circuit 12. The driverselection circuit 151 sets data signals transmitted from thetransmission circuit 13, as a plurality of input signals IN, and outputseach input signal IN to the corresponding transmission driver 152A.

One transmission driver 152A is provided for one linear electrode 32.The transmission driver 152A receives voltage GND (first voltage) from areference line W_GND, receives voltage VDD (second voltage) from a powersupply line W_VDD, amplifies the input signal IN input from the driverselection circuit 151, sets the amplified signal as a transmissionsignal OUT, and transmits the transmission signal OUT to thecorresponding linear electrode 32 through an output signal line Wout.The transmission driver 152A includes a first mode and a second mode.The transmission driver 152A in the first mode amplifies the signal tothe voltage difference from the voltage GND to the voltage VDD andoutputs the amplified signal as the transmission signal OUT. On theother hand, the transmission driver 152A in the second mode amplifiesthe signal to the voltage difference from the voltage GND (firstvoltage) to voltage (third voltage) that allows a signal to betransmitted from the linear electrode 32 and outputs the amplifiedsignal as the transmission signal OUT. Here, the voltage (third voltage)that allows a signal to be transmitted from the linear electrode 32 isvoltage higher than 5 V and higher than the voltage VDD (secondvoltage), such as approximately 9 V.

This completes the description of the configuration of the outputcircuit 15. Next, a configuration of circuits of the stylus 2 will bedescribed in detail. FIG. 4 depicts an example of a circuitconfiguration of the stylus 2 illustrated in FIG. 1 .

The stylus 2 includes, for example, an electrode 20, a selection circuit21, an oscillator 22, a transmission circuit 23, a reception circuit 24,a detection circuit 25, an input unit 26, a storage unit 27, acontroller 28, and a power supply 29.

The electrode 20 is a conductor in which charge corresponding to thedownlink signal DS or the uplink signal US is induced.

The selection circuit 21 is, for example, a multiplexer, and switchesthe state of connection between the electrode 20 and one of thetransmission circuit 23 and the reception circuit 24 according to aselection signal SEL input from the controller 28.

The oscillator 22 is an oscillation circuit that generates a carriersignal with a frequency used for communication between the touch sensormounted apparatus 3 and the stylus 2, according to a frequency settingsignal SEL_F input from the controller 28. The carrier signal may be asine wave or may be a square wave of a clock pulse.

The transmission circuit 23 generates the downlink signal DS inreference to the data input from the controller 28 and transmits thegenerated downlink signal DS to the touch sensor mounted apparatus 3through the electrode 20. The transmission circuit 23 includes thetransmission driver 152A. The transmission driver 152A amplifies thevoltage difference of the downlink signal DS to, for example, twice thepower supply voltage of the stylus 2 and transmits the downlink signalDS with the amplified voltage difference to the touch sensor mountedapparatus 3. The downlink signal DS with the voltage differenceamplified by the transmission driver 152A has voltage in which the lowlevel (first voltage) is, for example, 0 V and the high level (thirdvoltage) is equal to or greater than 15 V, such as approximately 20 V,and has a voltage difference of equal to or greater than 15 V, such as avoltage difference of approximately 20 V.

The reception circuit 24 detects and demodulates a change (signal) inthe amount of charge induced in the electrode 20 and outputs thedemodulated signal to the controller 28.

The detection circuit 25 acquires dynamic data that varies depending onthe operation state of the stylus 2, such as on/off or other operationstates of the input unit 26 that is a press button or the like providedon a side surface of the stylus 2, a value of pen pressure F detected byan unillustrated pen pressure detector, and remaining data of the powersupply 29 that is a drive power supply of the stylus 2, and outputs theacquired data to the controller 28.

The storage unit 27 stores configuration data which is static data thatdoes not vary depending on the operation state of the stylus 2, such asidentification information of the stylus 2, vendor informationindicating the manufacturer of the stylus 2, the type of the pen tip ofthe stylus 2 (such as a ballpoint pen and a brush), and the number ofinput units 26, and outputs the stored configuration data to thecontroller 28.

The controller 28 controls the transmission circuit 23 to transmit thedownlink signal DS in a time period instructed by the sensor controller10, based on the time of reception of the uplink signal US detected bythe reception circuit 24 after the start of an operation (pen-downoperation) of bringing the stylus 2 close to the touch sensor 30.

This completes the description of the configuration of the stylus 2.Next, a configuration of circuits of the transmission driver 152A willbe described in detail. FIG. 5 depicts an example of a circuitconfiguration of the transmission driver 152A according to the firstembodiment.

As illustrated in FIG. 5 , the transmission driver 152A includes, forexample, a signal generation circuit 153A, an output control circuit154, a NOT circuit INV1, a first booster circuit 155, and ashort-circuit control element SW1. Note that parasitic capacitance Coutin FIG. 5 is load capacitance connected to an output of the transmissiondriver 152A. Specifically, the parasitic capacitance Cout representscombined capacitance of the electrode 20 and the capacitance Cpen when,for example, the transmission driver 152A is mounted on the stylus 2 andrepresents combined capacitance of the linear electrode 32 of the touchsensor 30 and the capacitance Cpen when, for example, the transmissiondriver 152A is mounted on the sensor controller 10.

The signal generation circuit 153A generates a drive signal DRV and aboost signal BST1 according to the input signal IN that is input. Thesignal generation circuit 153A outputs the generated drive signal DRV(first signal) to the NOT circuit INV1 and the output control circuit154 and outputs the generated boost signal BST1 (second signal) to abuffer circuit BUF1 of the first booster circuit 155.

Specifically, the signal generation circuit 153A generates the drivesignal DRV (first signal) such that the voltage is shifted from the lowlevel (first voltage) to the high level (fourth voltage) at a firsttiming corresponding to the rise of the input signal IN and that thevoltage is shifted from the high level (fourth voltage) to the low level(first voltage) at a fourth timing that is a timing at which apredetermined time period has passed from a third timing correspondingto the fall of the input signal IN. The signal generation circuit 153Agenerates the boost signal BST1 such that the voltage is shifted fromthe low level (first voltage) to the high level (fifth voltage) at asecond timing that is a timing at which a predetermined time period haspassed from the first timing and that the voltage is shifted from thehigh level (fifth voltage) to the low level (first voltage) at the thirdtiming. The first timing here is, for example, a timing at which apredetermined clock has switched several times after the rise of theinput signal IN or a timing of a rise of a signal with a predetermineddelay from the input signal IN. The third timing is, for example, atiming at which a predetermined clock has switched several times afterthe fall of the input signal IN or a timing of a fall of a signal with apredetermined delay from the input signal IN.

The NOT circuit INV1 is, for example, an inverter circuit including atransistor, and functions as a control circuit that uses a controlsignal CT1 to control the short-circuit control element SW1. The NOTcircuit INV1 performs a NOT operation of the drive signal DRV input fromthe signal generation circuit 153A, sets the signal that has beensubjected to the operation, as the control signal CT1, and outputs thecontrol signal CT1 to a control terminal of the short-circuit controlelement SW1.

The first booster circuit 155 includes, for example, the buffer circuitBUF1 and a capacitive element Cext1. The first booster circuit 155boosts the voltage of a node connected to the output side, according tothe boost signal BST1 output from the signal generation circuit 153A,and supplies the boosted voltage (third voltage) to a positive powersupply terminal P of the output control circuit 154. Specifically, whenthe voltage of the boost signal BST1 output from the signal generationcircuit 153A is in the high level (fifth voltage), the first boostercircuit 155 boosts the voltage of the node connected to the output sideand supplies the boosted voltage to the positive power supply terminal Pof the output control circuit 154. On the other hand, when the voltageof the boost signal BST1 is in the low level (first voltage), the firstbooster circuit 155 stops the boost and supplies the voltage that hasnot been boosted (second voltage) to the positive power supply terminalP of the output control circuit 154.

The buffer circuit BUF1 is, for example, a buffer circuit including ametal oxide semiconductor (MOS) transistor. The buffer circuit BUF1enhances the boost signal BST1 output from the signal generation circuit153A and outputs the enhanced boost signal BST1 to the capacitiveelement Cext1. The buffer circuit BUF1 reduces or eliminates theelectrical effect that the capacitive element Cext1 and the signalgeneration circuit 153A exert on each other. Although the buffer circuitBUF1 is provided on the transmission driver 152A in the firstembodiment, the buffer circuit BUF1 may not be provided, and the boostsignal BST1 may directly be input from the signal generation circuit153A to one end of the capacitive element Cext1.

One end of the capacitive element Cext1 is connected to an outputterminal of the buffer circuit BUF1, and the other end of the capacitiveelement Cext1 is connected to the other end of the short-circuit controlelement SW1 and the positive power supply terminal P of the outputcontrol circuit 154. The capacitive element Cext1 supplies voltage VP2to the positive power supply terminal P of the output control circuit154. The capacitive element Cext1 receives the voltage VDD from thepower supply line W_VDD when the short-circuit control element SW1 isshort-circuited. The capacitance of the capacitive element Cext1 is, forexample, 1 to 10 uF and is typically 1 uF.

The short-circuit control element SW1 is, for example, a switch elementor a transistor. One end of the short-circuit control element SW1 isconnected to the power supply line W_VDD, and the other end of theshort-circuit control element SW1 is connected to the other end of thecapacitive element Cext1 and the positive power supply terminal P of theoutput control circuit 154. The short-circuit control element SW1short-circuits or opens both ends according to the control signal CT1input to the control terminal. Specifically, when the state of thecontrol signal CT1 is the high state, the short-circuit control elementSW1 short-circuits both ends and supplies the voltage VDD of the powersupply line W_VDD to the positive power supply terminal P of the outputcontrol circuit 154 and the capacitive element Cext1. On the other hand,when the state of the control signal CT1 is the low state, theshort-circuit control element SW1 opens both ends and stops the supplyof the voltage VDD of the power supply line W_VDD.

The output control circuit 154 enhances the drive signal DRV input fromthe signal generation circuit 153A to an input terminal I, according tothe voltage supplied to the positive power supply terminal P and thevoltage supplied to a negative power supply terminal M, and transmitsthe signal as the transmission signal OUT from an output terminal O tothe electrode 20 or the linear electrode 32. Specifically, the outputcontrol circuit 154 sets the voltage of the transmission signal OUT tothe voltage supplied to the positive power supply terminal P, when thestate of the drive signal DRV is the high state, and sets the voltage ofthe transmission signal OUT to the voltage supplied to the negativepower supply terminal M, when the state of the drive signal DRV is thelow state. The output control circuit 154 then outputs the transmissionsignal OUT from the output terminal O.

In the transmission driver 152A configured in this way, theshort-circuit control element SW1 short-circuits both ends when thestate of the drive signal DRV corresponding to the input signal IN isthe low state and opens both ends when the state of the drive signal DRVis the high state. While the short-circuit control element SW1 isshort-circuited, the operation mode of the transmission driver 152A isthe first mode. The voltage VDD (second voltage) is supplied from thepower supply line W_VDD to the positive power supply terminal P of theoutput control circuit 154 and the other end of the capacitive elementCext1, and the voltage GND (first voltage: such as 0 V) of the referenceline W_GND is supplied to one end of the capacitive element Cext1.

On the other hand, while the short-circuit control element SW1 is open,the operation mode of the transmission driver 152A is the second mode,and the short-circuit control element SW1 cuts off the supply of thevoltage VDD to the output control circuit 154. Voltage VP1 is suppliedfrom the other end of the capacitive element Cext1 to the positive powersupply terminal P of the output control circuit 154. While theshort-circuit control element SW1 is open, the voltage VP1 is voltageequivalent to the sum of the voltage VDD and the voltage of one end ofthe capacitive element Cext1 determined by the boost signal BST1corresponding to the input signal IN. Specifically, the voltage VP1 isthe voltage VDD (second voltage) when the voltage of one end of thecapacitive element Cext1 is the voltage GND, and the voltage VP1 is thevoltage (third voltage) that is twice the voltage VDD when the voltageof the capacitive element Cext1 is the voltage VDD.

The transmission driver 152A sets, as the transmission signal OUT, thevoltage supplied to the positive power supply terminal P of the outputcontrol circuit 154 or the voltage supplied to the negative power supplyterminal M of the output control circuit 154, according to the state ofthe input signal IN, and transmits the transmission signal OUT to theelectrode 20 or the linear electrode 32. That is, the transmissiondriver 152A generates the transmission signal OUT in which the voltageshifts to the voltage VDD (second voltage), the voltage (third voltage)that is twice the voltage VDD, and the voltage GND (first voltage),according to the input signal IN, and transmits the transmission signalOUT to the electrode 20 or the linear electrode 32.

Flow of a Series of Operations Regarding Transmission Driver

This completes the description of the configuration of the transmissiondriver 152A. Next, the shift in the voltage of each signal in thetransmission driver 152A will be described in detail. FIG. 6 is a timingchart illustrating an example of the shift in the voltage of each signalin the transmission driver 152A according to the first embodiment.

At time t60, the operation mode of the transmission driver 152A is thefirst mode. At time t60, the driver selection circuit 151 or thecontroller 28 shifts the voltage of the input signal IN from 0 V (firstvoltage) to the voltage VDD (fourth voltage). At time t60, the signalgeneration circuit 153A detects a rise in the voltage of the inputsignal IN. At time t60, the short-circuit control element SW1 isshort-circuited, and the voltage VDD is supplied from the power supplyline W_VDD to the positive power supply terminal P of the output controlcircuit 154 and the other end of the capacitive element Cext1. At timet60, the signal generation circuit 153A sets the voltage of the boostsignal BST1 to 0 V (first voltage) and outputs the boost signal BST1 tothe buffer circuit BUF1. Accordingly, the voltage VP1 is the voltage VDDat time t60. As a result, at time t60, the output control circuit 154sets the voltage of the transmission signal OUT to 0 V (first voltage)and transmits the transmission signal OUT to the electrode 20 or thelinear electrode 32.

At time t61, the signal generation circuit 153A shifts the voltage ofthe drive signal DRV from 0 V (first voltage) to the voltage VDD (fifthvoltage) according to a rise of the input signal IN. At time t61, theNOT circuit INV1 shifts the voltage of the control signal CT1 from thevoltage VDD (fifth voltage) to 0 V (first voltage). At time t61, bothends of the short-circuit control element SW1 are opened according tothe control signal CT1 in which the voltage is 0 V (first voltage). Attime t61, the supply of the voltage VDD (second voltage) from the powersupply line W_VDD to the positive power supply terminal P of the outputcontrol circuit 154 and the other end of the capacitive element Cext1stops. At time t61, the voltage VP1 is the voltage VDD (second voltage).At time t61, the output control circuit 154 shifts the voltage of thetransmission signal OUT from 0 V (first voltage) to the voltage VDD(second voltage) supplied to the positive power supply terminal P,according to the drive signal DRV.

At time t62, the operation mode of the transmission driver 152A isswitched from the first mode to the second mode. At time t62, the signalgeneration circuit 153A shifts the voltage of the boost signal BST1 from0 V (first voltage) to the voltage VDD (fifth voltage). At time t62, thebuffer circuit BUF1 shifts the voltage of one end of the capacitiveelement Cext1 from 0 V (first voltage) to the voltage VDD (fifthvoltage). In association with this, the capacitive element Cext1 triesto hold the voltage difference between the two ends, and the voltage VP1of the other end of the capacitive element Cext1 shifts at time t62 fromthe voltage VDD (second voltage) to the voltage (third voltage:2×voltage VDD) equivalent to the sum of the voltage VDD and the voltage(fifth voltage: voltage VDD) of one end of the capacitive element Cext1.As a result, at time t62, the output control circuit 154 shifts thevoltage of the transmission signal OUT from the voltage VDD (secondvoltage) to the voltage VP1 (third voltage: 2×voltage VDD) supplied tothe positive power supply terminal P.

At time t63, the driver selection circuit 151 or the controller 28shifts the voltage of the input signal IN from the voltage VDD (fourthvoltage) to 0 V (first voltage). At time t63, the signal generationcircuit 153A detects a fall in the voltage of the input signal IN. Attime t63, the output control circuit 154 keeps the voltage of thetransmission signal OUT set to the voltage VP1 (third voltage: 2×voltageVDD) and transmits the transmission signal OUT to the electrode 20 orthe linear electrode 32.

At time t64, the operation mode of the transmission driver 152A isswitched from the second mode to the first mode. At time t64, the signalgeneration circuit 153A shifts the voltage of the boost signal BST1 fromthe voltage VDD (fifth voltage) to 0 V (first voltage). At time t64, thebuffer circuit BUF1 shifts the voltage of one end of the capacitiveelement Cext1 from the voltage VDD (fifth voltage) to 0 V (firstvoltage). In association with this, the capacitive element Cext1 triesto hold the voltage difference between the two ends, and the voltage VP1of the other end of the capacitive element Cext1 shifts at time t64 fromthe voltage (third voltage) that is twice the voltage VDD to the voltageVDD (second voltage). As a result, at time t64, the output controlcircuit 154 shifts the voltage of the transmission signal OUT from thevoltage (third voltage) that is twice the voltage VDD to the voltage VP1(second voltage: voltage VDD) supplied to the positive power supplyterminal P.

At time t65, the signal generation circuit 153A shifts the voltage ofthe drive signal DRV from the voltage VDD (fifth voltage) to 0 V (firstvoltage), according to the fall of the input signal IN. At time t65, theNOT circuit INV1 shifts the voltage of the control signal CT1 from 0 V(first voltage) to the voltage VDD (fourth voltage). At time t65, bothends of the short-circuit control element SW1 are short-circuitedaccording to the control signal CT1 in which the voltage is the voltageVDD (fourth voltage). At time t65, the voltage VDD (second voltage) issupplied from the power supply line W_VDD to the positive power supplyterminal P of the output control circuit 154 and the other end of thecapacitive element Cext1. At time t65, the voltage VP1 is the voltageVDD (second voltage). At time t65, the output control circuit 154 shiftsthe voltage of the transmission signal OUT from the voltage VDD (secondvoltage) to 0 V (first voltage) supplied to the negative power supplyterminal M, according to the drive signal DRV.

Note that the time period from time t61 to time t62 is typically equalto or smaller than half the time period from time t61 to time t63 andthe time period from time t63 to time t64 is typically equal to orsmaller than half the time period from time t62 to time t64.

This completes the description of the example of the shift in thevoltage of each signal in the transmission driver 152A. Next, a flow ofa series of processes of an electronic device (stylus 2 or touch sensormounted apparatus 3) including the transmission driver 152A will bedescribed in detail. FIG. 7 is a flow chart illustrating an example of aflow of a series of processes of the electronic device including thetransmission driver 152A according to the first embodiment.

(Step SP10)

In the electronic device, the signal generation circuit 153A of thetransmission driver 152A determines whether or not the signal waveformof the input signal IN is rising. If the electronic device determinesthat the signal waveform of the input signal IN is rising, the processmoves to a process of step SP12. On the other hand, if the electronicdevice determines that the signal waveform of the input signal IN is notrising, the process moves to a process of step SP18.

(Step SP12)

The operation mode of the electronic device is the first mode. In theelectronic device in the first mode, the transmission driver 152Atransmits the transmission signal OUT with the voltage in a range from 0V (first voltage) to the voltage VDD (second voltage). The electronicdevice causes the signal generation circuit 153A to shift the voltage ofthe drive signal DRV from 0 V (first voltage) to the voltage VDD (fourthvoltage) and outputs the drive signal DRV to the output control circuit154. The electronic device then causes the output control circuit 154 toshift the voltage of the transmission signal OUT from 0 V (firstvoltage) to the voltage VDD (second voltage). The process then moves toa process of step SP14.

(Step SP14)

The electronic device opens the short-circuit control element SW1 tostop the supply of the voltage VDD (second voltage) from the powersupply line W_VDD to the positive power supply terminal P of the outputcontrol circuit 154 and the other end of the capacitive element Cext1.The process then moves to a process of step SP16.

(Step SP16)

The electronic device switches the operation mode from the first mode tothe second mode. The electronic device causes the signal generationcircuit 153A to shift the voltage of the boost signal BST1 from 0 V(first voltage) to the voltage VDD (fifth voltage) and outputs the boostsignal BST1 to the buffer circuit BUF1. In association with this, thevoltage VP1 of the other end of the capacitive element Cext1 shifts fromthe voltage VDD (second voltage) to the voltage (third voltage) that istwice the voltage VDD, and the voltage (third voltage) that is twice thevoltage VDD is supplied to the positive power supply terminal P of theoutput control circuit 154. As a result, the electronic device causesthe output control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage VDD (second voltage) to the voltage (thirdvoltage) that is twice the voltage VDD. The process then moves to aprocess of step SP18.

(Step SP18)

In the electronic device, the signal generation circuit 153A of thetransmission driver 152A determines whether or not the signal waveformof the input signal IN is falling. If the electronic device determinesthat the signal waveform of the input signal IN is falling, the processmoves to a process of step SP20. On the other hand, if the electronicdevice determines that the signal waveform of the input signal IN is notfalling, the process ends the series of processes in FIG. 7 .

(Step SP20)

The operation mode of the electronic device is the second mode. In theelectronic device in the second mode, the transmission driver 152Atransmits the transmission signal OUT with the voltage in a range from 0V (first voltage) to the voltage (third voltage) higher than the voltageVDD (second voltage). The electronic device then switches the operationmode from the second mode to the first mode. The electronic devicecauses the signal generation circuit 153A to shift the voltage of theboost signal BST1 from the voltage VDD (fifth voltage) to 0 V (firstvoltage) and outputs the boost signal BST1 to the buffer circuit BUF1.In association with this, the voltage VP1 of the other end of thecapacitive element Cext1 shifts from the voltage (third voltage) that istwice the voltage VDD to the voltage VDD (second voltage), and thevoltage VDD (second voltage) is supplied to the positive power supplyterminal P of the output control circuit 154. As a result, theelectronic device causes the output control circuit 154 to shift thevoltage of the transmission signal OUT from the voltage (third voltage)that is twice the voltage VDD to the voltage VDD (second voltage). Theprocess then moves to a process of step SP22.

(Step SP22)

The electronic device causes the signal generation circuit 153A to shiftthe voltage of the drive signal DRV from the voltage VDD (fourthvoltage) to 0 V (first voltage) and outputs the drive signal DRV to theoutput control circuit 154. The electronic device then causes the outputcontrol circuit 154 to shift the voltage of the transmission signal OUTfrom the voltage VDD (second voltage) to 0 V (first voltage). Theprocess then moves to a process of step SP24.

(Step SP24)

The electronic device short-circuits the short-circuit control elementSW1 to supply the voltage VDD (second voltage) from the power supplyline W_VDD to the positive power supply terminal P of the output controlcircuit 154 and the other end of the capacitive element Cext1.

Effects

In the first embodiment, the transmission driver 152A receives the inputsignal IN, the voltage GND (first voltage), and the voltage VDD (secondvoltage) and transmits the transmission signal OUT according to theinput signal IN. The transmission driver 152A includes the first mode oftransmitting the transmission signal OUT with the voltage in the rangefrom the voltage GND (first voltage) to the voltage VDD (second voltage)and the second mode of transmitting the transmission signal OUT with thevoltage in the range from the voltage GND (first voltage) to the voltage(third voltage) higher than the voltage VDD (second voltage).

According to the configuration, the transmission driver 152A can outputthe transmission signal OUT with the voltage (third voltage) higher thanthe supplied voltage VDD (second voltage), and the voltage of the powersupply that supplies the voltage VDD does not have to be higher than thevoltage VDD. Thus, the transmission driver 152A can independently reducethe power consumption.

In the first embodiment, the transmission driver 152A further includesthe first booster circuit 155 that supplies the voltage (third voltage)higher than the voltage VDD (second voltage).

According to the configuration, the transmission driver 152A can supplythe voltage (third voltage) higher than the voltage VDD (second voltage)supplied by the first booster circuit 155, and the voltage of the powersupply that supplies the voltage VDD does not have to be higher than thevoltage VDD. Thus, the transmission driver 152A can independently reducethe power consumption.

In the first embodiment, the transmission driver 152A further includesthe output control circuit 154 that receives the voltage GND (firstvoltage) and one of the voltage VDD (second voltage) and the voltage(third voltage) higher than the voltage VDD and that outputs thetransmission signal OUT from the output terminal O, and theshort-circuit control element SW1 that controls the supply of thevoltage VDD (second voltage) to the output control circuit 154.

According to the configuration, the short-circuit control element SW1 inthe transmission driver 152A can control the supply of voltage to theoutput control circuit 154. Thus, the transmission driver 152A canindependently reduce the power consumption with a simple configuration.

In the first embodiment, the first booster circuit 155 includes thecapacitive element Cext1.

According to the configuration, the capacitive element Cext1 in thetransmission driver 152A realizes boosting. Thus, the transmissiondriver 152A can independently reduce the power consumption with a simpleconfiguration.

In the transmission driver 152A of the first embodiment, the voltage VDD(second voltage) is supplied to the output control circuit 154 throughthe short-circuit control element SW1 in the first mode. In the secondmode, the short-circuit control element SW1 cuts off the supply of thevoltage VDD (second voltage) to the output control circuit 154, and thefirst booster circuit 155 supplies the voltage (third voltage) higherthan the voltage VDD to the output control circuit 154.

According to the configuration, the short-circuit control element SW1 inthe transmission driver 152A can control the supply of voltage to theoutput control circuit 154. Thus, the transmission driver 152A canindependently reduce the power consumption with a simple configuration.

In the first embodiment, the output control circuit 154 includes thepositive power supply terminal P and the negative power supply terminalM, the voltage GND (first voltage) is supplied to the negative powersupply terminal M, the voltage VDD (second voltage) is supplied to oneend of the short-circuit control element SW1, and the other end of theshort-circuit control element SW1 and one end of the capacitive elementCext1 are connected to the positive power supply terminal P.

According to the configuration, the capacitive element Cext1 in thetransmission driver 152A realizes boosting. Thus, the transmissiondriver 152A can independently reduce the power consumption with a simpleconfiguration.

In the first embodiment, the transmission driver 152A further includesthe signal generation circuit 153A that generates the drive signal DRV(first signal) and the boost signal BST1 (second signal) according tothe input signal IN. The output control circuit 154 sets the voltagesupplied to the positive power supply terminal P or the voltage (firstvoltage) supplied to the negative power supply terminal M, as thetransmission signal OUT, according to the drive signal DRV (firstsignal), and outputs the transmission signal OUT. The boost signal BST1(second signal) is input to the other end of the capacitive elementCext1.

According to the configuration, the voltage of one end of the capacitiveelement Cext1 in the transmission driver 152A is determined by thevoltage of the boost signal BST1. When both ends of the short-circuitcontrol element SW1 are open, the capacitive element Cext1 tries tomaintain the voltage difference between the two ends. Hence, the voltageVP1 of the other end of the capacitive element Cext1 is determined bythe voltage of one end of the capacitive element Cext1. That is, if thevoltage of one end of the capacitive element Cext1 is raised when thevoltage VP1 of the other end of the capacitive element Cext1 is thevoltage VDD, the voltage VP1 of the other end of the capacitive elementCext1 exceeds the voltage VDD. As a result, the transmission driver 152Acan output, as the transmission signal OUT, the voltage exceeding thevoltage VDD of the power supply line W_VDD from the output controlcircuit 154, and the voltage of the power supply line W_VDD can besuppressed. Thus, the transmission driver 152A independently realizesthe reduction in power consumption.

In the first embodiment, the transmission driver 152A further includesthe NOT circuit INV1 (control circuit) that controls the short-circuitcontrol element SW1 to short-circuit the short-circuit control elementSW1 when the voltage of the drive signal DRV (first signal) is thevoltage GND (first voltage) and to open the short-circuit controlelement SW1 when the voltage of the drive signal DRV (first signal) isthe voltage VDD (fourth voltage). The signal generation circuit 153Agenerates the drive signal DRV (first signal) such that the voltage isshifted from the voltage GND (first voltage) to the voltage VDD (fourthvoltage) at the first timing (time t61) corresponding to the rise of theinput signal IN and that the voltage is shifted from the voltage VDD(fourth voltage) to the voltage GND (first voltage) at the fourth timing(time t65) that is a timing at which a predetermined time period haspassed from the third timing (time t64) corresponding to the fall of theinput signal IN. The signal generation circuit 153A generates the boostsignal BST1 (second signal) such that the voltage is shifted from thevoltage GND (first voltage) to the voltage VDD (fifth voltage) at thesecond timing (time t62) that is a timing at which a predetermined timeperiod has passed from the first timing (time t61) and that the voltageis shifted from the voltage VDD (fifth voltage) to the voltage GND(first voltage) at the third timing (time t64).

According to the configuration, the transmission driver 152A supplies 0V to one end of the capacitive element Cext1 and supplies the voltageVDD from the power supply line W_VDD to the other end of the capacitiveelement Cext1. The transmission driver 152A then stops the supply of thevoltage VDD from the power supply line W_VDD to the other end of thecapacitive element Cext1. The transmission driver 152A further raisesthe voltage of one end of the capacitive element Cext1 from 0 V to thevoltage VDD to increase the voltage VP1 of the other end of thecapacitive element Cext1 to the voltage twice the voltage VDD andsupplies the increased voltage VP1 to the positive power supply terminalP of the output control circuit 154. In this way, the transmissiondriver 152A can output, as the transmission signal OUT, the voltagetwice the voltage VDD of the power supply line W_VDD from the outputcontrol circuit 154, and the voltage of the power supply line W_VDD canbe suppressed. Thus, the transmission driver 152A independently realizesthe reduction in power consumption.

In the first embodiment, the time period from the first timing (timet61) to the second timing (time t62) is equal to or smaller than halfthe time period from the first timing (time t61) to the third timing(time t63). The time period from the third timing (time t63) to thefourth timing (time t64) is equal to or smaller than half the timeperiod from the second timing (time t62) to the fourth timing (timet64).

In the first embodiment, the fourth voltage and the fifth voltage areequal to the voltage VDD (second voltage) of the power supply lineW_VDD.

According to the configuration, the transmission driver 152A can outputthe transmission signal OUT with the voltage exceeding the voltage VDDof the power supply line W_VDD, even when the power supply system isone. Thus, the transmission driver 152A independently realizes thereduction in power consumption.

In the first embodiment, the capacitance of the capacitive element Cext1is equal to or greater than ten times the parasitic capacitance Coutconnected to the output terminal O. Specifically, while the capacitanceof the parasitic capacitance Cout is smaller than 10 pF, the capacitanceof the capacitive element Cext1 is 1 to 10 uF.

In the first embodiment, the electronic device (stylus 2 or touch sensormounted apparatus 3) includes the electrode 20 or the linear electrode32 that transmits and receives signals, and the transmission driver 152Athat receives the input signal IN, the voltage GND (first voltage), andthe voltage VDD (second voltage) and that transmits the transmissionsignal OUT according to the input signal IN. In the electronic device,the transmission driver 152A includes the first mode of transmitting thetransmission signal OUT with the voltage ranging from the voltage GND(first voltage) to the voltage VDD (second voltage) and the second modeof transmitting the transmission signal OUT with the voltage rangingfrom the voltage GND (first voltage) to the voltage (third voltage)higher than the voltage VDD (second voltage).

According to the configuration, the electronic device (stylus 2 or touchsensor mounted apparatus 3) provided with the transmission driver 152Acan reduce the power consumption.

In the first embodiment, the transmission driver 152A is mounted on thestylus 2. The electrode 20 is a stylus side electrode that transmits andreceives signals through capacitive coupling between the electrode 20and the sensor side electrode connected to the sensor controller 10, andthe electrode 20 is mounted on the stylus 2.

According to the configuration, the stylus 2 can reduce the powerconsumption.

In the first embodiment, the electronic device (touch sensor mountedapparatus 3) includes the touch sensor 30 including the plurality oflinear electrodes 32 arranged in a plane shape, and the sensorcontroller 10 that includes the plurality of transmission drivers 152Aconfigured to transmit the transmission signals OUT to the correspondinglinear electrodes 32 and that is connected to the touch sensor 30.

According to the configuration, the touch sensor mounted apparatus 3 canreduce the power consumption.

Second Embodiment

This completes the description of the first embodiment. Next, a secondembodiment will be described.

Circuit Configuration

FIG. 8 depicts an example of a circuit configuration of a transmissiondriver 152B according to the second embodiment. As illustrated in FIG. 8, the transmission driver 152B further includes, for example, a secondbooster circuit 156 and a NOT circuit INV2, as compared to thetransmission driver 152A. The transmission driver 152B includes a signalgeneration circuit 153B in place of the signal generation circuit 153A,as compared to the transmission driver 152A. Note that, in thedescription of the circuit configuration of the transmission driver152B, the description of components similar to the components of thetransmission driver 152A will appropriately be skipped.

The signal generation circuit 153B generates the drive signal DRV andboost signals BST1 and BST2 according to the input signal IN that isinput. The signal generation circuit 153B outputs the generated drivesignal DRV to the NOT circuit INV1 and the output control circuit 154,outputs the generated boost signal BST1 to the NOT circuit INV2 and thebuffer circuit BUF1 of the first booster circuit 155, and outputs thegenerated boost signal BST2 to the buffer circuit BUF2 of the secondbooster circuit 156.

Specifically, the signal generation circuit 153B generates the drivesignal DRV such that the voltage is shifted from the low level (firstvoltage) to the high level (fourth voltage) at the first timing and thatthe voltage is shifted from the high level (fourth voltage) to the lowlevel (first voltage) at the fourth timing. The signal generationcircuit 153B generates the boost signal BST1 such that the voltage isshifted from the low level (first voltage) to the high level (fifthvoltage) at the second timing and that the voltage is shifted from thehigh level (fifth voltage) to the low level (first voltage) at the thirdtiming.

The signal generation circuit 153B generates the boost signal BST2 suchthat the voltage is shifted from the low level to the high level at afifth timing that is a timing in a period from the second timing to thethird timing and that the voltage is shifted from the high level to thelow level at a sixth timing that is a timing in a period from the fifthtiming to the third timing.

The NOT circuit INV2 is, for example, an inverter circuit including atransistor, and functions as a control circuit that uses a controlsignal CT2 to control a short-circuit control element SW2. The NOTcircuit INV2 performs a NOT operation of the boost signal BST1 inputfrom the signal generation circuit 153B, sets the signal that has beensubjected to the operation, as the control signal CT2, and outputs thecontrol signal CT2 to a control terminal of the short-circuit controlelement SW2.

The second booster circuit 156 includes, for example, a buffer circuitBUF2 and a capacitive element Cext2. The second booster circuit 156supplies, to the first booster circuit 155, voltage (seventh voltage)higher than 0 V (first voltage) by a difference between the voltage(third voltage) that is twice the voltage VDD and the voltage VDD(second voltage) or voltage (eighth voltage) higher than 0 V (firstvoltage) by a difference between voltage (sixth voltage) that is threetimes the voltage VDD and the voltage VDD (second voltage).Specifically, when the voltage of the boost signal BST2 output from thesignal generation circuit 153B is in the high level, the second boostercircuit 156 boosts the voltage of a node connected to the output sideand supplies the boosted voltage (eighth voltage) to a power supplyterminal of the buffer circuit BUF1 in the first booster circuit 155. Onthe other hand, when the voltage of the boost signal BST2 is in the lowlevel, the second booster circuit 156 stops the boost and supplies thevoltage (seventh voltage) that has not been boosted to the power supplyterminal of the buffer circuit BUF1 in the first booster circuit 155.

The buffer circuit BUF2 is, for example, a buffer circuit including aMOS transistor. The buffer circuit BUF2 enhances the boost signal BST2output from the signal generation circuit 153B and outputs the enhancedboost signal BST2 to the capacitive element Cext2. The buffer circuitBUF2 reduces or eliminates the electrical effect that the capacitiveelement Cext2 and the signal generation circuit 153B exert on eachother. Although the buffer circuit BUF2 is provided on the transmissiondriver 152B in the second embodiment, the buffer circuit BUF2 may not beprovided, and the boost signal BST2 may directly be input from thesignal generation circuit 153B to one end of the capacitive elementCext2.

One end of the capacitive element Cext2 is connected to an outputterminal of the buffer circuit BUF2, and the other end of the capacitiveelement Cext2 is connected to the other end of the short-circuit controlelement SW2 and the power supply terminal of the buffer circuit BUF1 inthe first booster circuit 155. The capacitive element Cext2 supplies thevoltage VP2 (seventh voltage or eighth voltage) to the power supplyterminal of the buffer circuit BUF1 in the first booster circuit 155.The capacitive element Cext2 receives the voltage VDD from the powersupply line W_VDD when the short-circuit control element SW2 isshort-circuited. The capacitance of the capacitive element Cext2 is, forexample, 1 to 10 uF and is typically 1 uF.

The short-circuit control element SW2 is, for example, a switch elementor a transistor. One end of the short-circuit control element SW2 isconnected to the power supply line W_VDD, and the other end of theshort-circuit control element SW2 is connected to the other end of thecapacitive element Cext2 and the power supply terminal of the buffercircuit BUF1 in the first booster circuit 155. The short-circuit controlelement SW2 short-circuits or opens both ends according to the controlsignal CT2 input to the control terminal. Specifically, when the stateof the control signal CT2 is the high state, the short-circuit controlelement SW2 short-circuits both ends and supplies the voltage VDD(seventh voltage) of the power supply line W_VDD to the power supplyterminal of the buffer circuit BUF1 in the first booster circuit 155 andthe capacitive element Cext2. On the other hand, when the state of thecontrol signal CT2 is the low state, the short-circuit control elementSW2 opens both ends and stops the supply of the voltage VDD of the powersupply line W_VDD.

In the transmission driver 152B configured in this way, theshort-circuit control element SW1 short-circuits both ends when thestate of the drive signal DRV corresponding to the input signal IN isthe low state and opens both ends when the state of the drive signal DRVis the high state. While the short-circuit control element SW1 isshort-circuited, the operation mode of the transmission driver 152B isthe first mode. The voltage VDD (second voltage) is supplied from thepower supply line W_VDD to the positive power supply terminal P of theoutput control circuit 154 and the other end of the capacitive elementCext1, and the voltage GND (first voltage) is supplied to one end of thecapacitive element Cext1.

While the short-circuit control element SW1 is open but theshort-circuit control element SW2 is short-circuited, the operation modeof the transmission driver 152B is the second mode. The short-circuitcontrol element SW1 cuts off the supply of the voltage VDD to the outputcontrol circuit 154, and the voltage VP1 is supplied from the other endof the capacitive element Cext1 to the positive power supply terminal Pof the output control circuit 154. While the short-circuit controlelement SW1 is open but the short-circuit control element SW2 isshort-circuited, the voltage VP1 is voltage equivalent to the sum of thevoltage VDD and the voltage of one end of the capacitive element Cext1determined by the boost signal BST1 corresponding to the input signalIN. Specifically, the voltage VP1 is the voltage VDD (second voltage)when the voltage of one end of the capacitive element Cext1 is thevoltage GND, and the voltage VP1 is the voltage (third voltage) that istwice the voltage VDD, when the voltage of one end of the capacitiveelement Cext1 is the voltage VDD.

While both the short-circuit control elements SW1 and SW2 are open, theoperation mode of the transmission driver 152B is the third mode. Theshort-circuit control element SW1 cuts off the supply of the voltage VDDto the output control circuit 154, and the voltage VP1 is supplied fromthe other end of the capacitive element Cext1 to the positive powersupply terminal P of the output control circuit 154. The short-circuitcontrol element SW2 cuts off the supply of the voltage VDD (seventhvoltage) to the power supply terminal of the buffer circuit BUF1 in thefirst booster circuit 155, and the voltage VP2 (seventh voltage) issupplied from the other end of the capacitive element Cext2 to the powersupply terminal of the buffer circuit BUF1 in the first booster circuit155.

While both the short-circuit control elements SW1 and SW2 are open, thevoltage VP2 is voltage equivalent to the sum of the voltage VDD and thevoltage of one end of the capacitive element Cext2 determined by theboost signal BST2 corresponding to the input signal IN. Specifically,the voltage VP2 is the voltage VDD (seventh voltage) when the voltage ofone end of the capacitive element Cext2 is the voltage GND, and thevoltage VP2 is the voltage (eighth voltage) that is twice the voltageVDD, when the voltage of one end of the capacitive element Cext2 is thevoltage VDD.

While both the short-circuit control elements SW1 and SW2 are open, thevoltage VP1 is voltage equivalent to the sum of the voltage VDD and thevoltage of one end of the capacitive element Cext1 determined by theboost signals BST1 and BST2 corresponding to the input signal IN.Specifically, the voltage VP1 is the voltage VDD (second voltage) whenthe voltage of one end of the capacitive element Cext1 is the voltageGND. On the other hand, the voltage VP1 is voltage equivalent to the sumof the voltage VP2 and the voltage VDD, that is, the voltage (thirdvoltage) that is twice the voltage VDD or the voltage (sixth voltage)that is three times the voltage VDD, when the voltage of one end of thecapacitive element Cext1 is the voltage VP2 (potential VDD or voltagetwice the voltage VDD).

The transmission driver 152B sets, as the transmission signal OUT, thevoltage supplied to the positive power supply terminal P of the outputcontrol circuit 154 or the voltage supplied to the negative power supplyterminal M of the output control circuit 154, according to the state ofthe input signal IN, and transmits the transmission signal OUT to theelectrode 20 or the linear electrode 32. That is, the transmissiondriver 152B generates the transmission signal OUT in which the voltageshifts to the voltage VDD (second voltage), the voltage (third voltage)that is twice the voltage VDD, the voltage (sixth voltage) that is threetimes the voltage VDD, and the voltage GND (first voltage), according tothe input signal IN, and transmits the transmission signal OUT to theelectrode 20 or the linear electrode 32.

Flow of a Series of Operations Regarding Transmission Driver

This completes the description of the configuration of the transmissiondriver 152B. Next, the shift in the voltage of each signal in thetransmission driver 152B will be described in detail. FIG. 9 is a timingchart illustrating an example of the shift in the voltage of each signalin the transmission driver 152B according to the second embodiment.

At time t91, the operation mode of the transmission driver 152B is thefirst mode. At time t91, the driver selection circuit 151 or thecontroller 28 shifts the voltage of the input signal IN from 0 V to thevoltage VDD. At time t91, the signal generation circuit 153B detects arise in the voltage of the input signal IN. At time t91, theshort-circuit control element SW1 is short-circuited, and the voltageVDD is supplied from the power supply line W_VDD to the positive powersupply terminal P of the output control circuit 154 and the other end ofthe capacitive element Cext1. At time t91, the short-circuit controlelement SW2 is short-circuited, and the voltage VDD is supplied from thepower supply line W_VDD to the power supply terminal of the buffercircuit BUF1 in the first booster circuit 155 and the other end of thecapacitive element Cext2. At time t91, the signal generation circuit153B sets the voltage of the boost signal BST1 to 0 V and outputs theboost signal BST1 to the buffer circuit BUF1. Accordingly, the voltageof the voltage VP1 is the voltage VDD (second voltage) at time t91. Thevoltage of the voltage VP2 is the voltage VDD (seventh voltage) at timet91. As a result, at time t91, the output control circuit 154 sets thevoltage of the transmission signal OUT to 0 V (first voltage) andtransmits the transmission signal OUT to the electrode 20 or the linearelectrode 32.

At time t92, the signal generation circuit 153B shifts the voltage ofthe drive signal DRV from 0 V to the voltage VDD according to a rise ofthe input signal IN. At time t92, the NOT circuit INV1 shifts thevoltage of the control signal CT1 from the voltage VDD to 0 V. At timet92, both ends of the short-circuit control element SW1 are openedaccording to the control signal CT1 in which the voltage is 0 V. At timet92, the supply of the voltage VDD (second voltage) from the powersupply line W_VDD to the positive power supply terminal P of the outputcontrol circuit 154 and the other end of the capacitive element Cext1stops. Accordingly, the voltage of the voltage VP1 is the voltage VDD(second voltage) at time t92. The voltage of the voltage VP2 is thevoltage VDD (seventh voltage) at time t92. At time t92, the outputcontrol circuit 154 shifts the voltage of the transmission signal OUTfrom 0 V (first voltage) to the voltage VDD (second voltage) supplied tothe positive power supply terminal P, according to the drive signal DRV.

At time t93, the operation mode of the transmission driver 152B isswitched from the first mode to the second mode. At time t93, the signalgeneration circuit 153B shifts the voltage of the boost signal BST1 from0 V to the voltage VDD. At time t93, the NOT circuit INV2 shifts thevoltage of the control signal CT2 from the voltage VDD to 0 V. At timet93, both ends of the short-circuit control element SW2 are openedaccording to the control signal CT2 in which the voltage is 0 V. At timet93, the supply of the voltage VDD (second voltage) from the powersupply line W_VDD to the power supply terminal of the buffer circuitBUF1 in the first booster circuit 155 and the other end of thecapacitive element Cext2 stops. At time t93, the voltage of the voltageVP2 is the voltage VDD (seventh voltage). At time t93, the buffercircuit BUF1 shifts the voltage of one end of the capacitive elementCext1 from 0 V to the voltage VDD. In association with this, thecapacitive element Cext1 tries to hold the voltage difference betweenthe two ends, and the voltage VP1 of the other end of the capacitiveelement Cext1 shifts at time t93 from the voltage VDD (second voltage)to the voltage (third voltage: 2×voltage VDD) equivalent to the sum ofthe voltage VDD and the voltage (potential VDD) of one end of thecapacitive element Cext1. As a result, at time t93, the output controlcircuit 154 shifts the voltage of the transmission signal OUT from thevoltage VDD (second voltage) to the voltage (third voltage) that istwice the voltage VDD.

At time t94, the operation mode of the transmission driver 152B isswitched from the second mode to the third mode. At time t94, the signalgeneration circuit 153B shifts the voltage of the boost signal BST2 from0 V to the voltage VDD. At time t94, the buffer circuit BUF2 shifts thevoltage of one end of the capacitive element Cext2 from 0 V to thevoltage VDD. In association with this, the capacitive element Cext2tries to hold the voltage difference between the two ends, and thevoltage VP2 of the other end of the capacitive element Cext2 shifts attime t94 from the voltage VDD (seventh voltage) to the voltage (eighthvoltage: 2×voltage VDD) equivalent to the sum of the voltage VDD and thevoltage (potential VDD) of one end of the capacitive element Cext2. Attime t94, the buffer circuit BUF1 shifts the voltage of one end of thecapacitive element Cext1 from the voltage VDD (seventh voltage) to thevoltage (eighth voltage: 2×voltage VDD) equivalent to the sum of thevoltage VDD and the voltage (potential VDD) of one end of the capacitiveelement Cext2. In association with this, the capacitive element Cext1tries to hold the voltage difference between the two ends, and thevoltage VP1 of the other end of the capacitive element Cext1 shifts attime t94 from the third voltage (2×voltage VDD) to the voltage (sixthvoltage: 3×voltage VDD) equivalent to the sum of the voltage VDD and thevoltage (2×voltage VDD) of one end of the capacitive element Cext1. As aresult, the output control circuit 154 shifts the voltage of thetransmission signal OUT from the voltage (third voltage) that is twicethe voltage VDD to the voltage (sixth voltage) that is three times thevoltage VDD.

At time t95, the driver selection circuit 151 or the controller 28shifts the voltage of the input signal IN from the voltage VDD to 0 V.At time t95, the signal generation circuit 153B detects a fall in thevoltage of the input signal IN. At time t95, the output control circuit154 keeps the voltage of the transmission signal OUT set to the voltage(sixth voltage) that is three times the voltage VDD and transmits thetransmission signal OUT to the electrode 20 or the linear electrode 32.

At time t96, the operation mode of the transmission driver 152B isswitched from the third mode to the second mode. At time t96, the signalgeneration circuit 153B shifts the voltage of the boost signal BST2 fromthe voltage VDD to 0 V. At time t96, the buffer circuit BUF2 shifts thevoltage of one end of the capacitive element Cext2 from the voltage VDDto 0 V. In association with this, the capacitive element Cext2 tries tohold the voltage difference between the two ends, and the voltage VP2 ofthe other end of the capacitive element Cext2 shifts at time t96 fromthe voltage (eighth voltage) that is twice the voltage VDD to thevoltage VDD (seventh voltage). At time t96, the buffer circuit BUF1shifts the voltage of one end of the capacitive element Cext1 from thevoltage (eighth voltage) that is twice the voltage VDD to the voltageVDD (seventh voltage). In association with this, the capacitive elementCext1 tries to hold the voltage difference between the two ends, and thevoltage VP1 of the other end of the capacitive element Cext1 shifts attime t96 from the voltage (sixth voltage) that is three times thevoltage VDD to the voltage (third voltage) that is twice the voltageVDD. As a result, at time t96, the output control circuit 154 shifts thevoltage of the transmission signal OUT from the voltage (sixth voltage)that is three times the voltage VDD to the voltage (third voltage) thatis twice the voltage VDD.

At time t97, the operation mode of the transmission driver 152B isswitched from the second mode to the first mode. At time t97, the signalgeneration circuit 153B shifts the voltage of the boost signal BST1 fromthe voltage VDD to 0 V. At time t97, the NOT circuit INV2 shifts thevoltage of the control signal CT2 from 0 V to the voltage VDD. At timet97, both ends of the short-circuit control element SW2 areshort-circuited according to the control signal CT2 in which the voltageis the voltage VDD. At time t97, the voltage VDD is supplied from thepower supply line W_VDD to the power supply terminal of the buffercircuit BUF1 in the first booster circuit 155 and the other end of thecapacitive element Cext2. At time t97, the buffer circuit BUF1 shiftsthe voltage of one end of the capacitive element Cext1 from the voltageVDD to 0 V. In association with this, the capacitive element Cext1 triesto hold the voltage difference between the two ends, and the voltage VP1of the other end of the capacitive element Cext1 shifts at time t97 fromthe voltage (third voltage) that is twice the voltage VDD to the voltageVDD (second voltage). As a result, at time t97, the output controlcircuit 154 shifts the voltage of the transmission signal OUT from thevoltage (third voltage) that is twice the voltage VDD to the voltage VDD(second voltage).

At time t98, the signal generation circuit 153B shifts the voltage ofthe drive signal DRV from the voltage VDD to 0 V according to a fall ofthe input signal IN. At time t98, the NOT circuit INV1 shifts thevoltage of the control signal CT1 from 0 V to the voltage VDD. At timet98, both ends of the short-circuit control element SW1 areshort-circuited according to the control signal CT1 in which the voltageis the voltage VDD. At time t98, the voltage VDD (second voltage) issupplied from the power supply line W_VDD to the positive power supplyterminal P of the output control circuit 154 and the other end of thecapacitive element Cext1. At time t98, the voltage VP1 is the voltageVDD (second voltage). At time t98, the output control circuit 154 shiftsthe voltage of the transmission signal OUT from the voltage VDD (secondvoltage) to 0 V (first voltage) supplied to the negative power supplyterminal M, according to the drive signal DRV.

Note that the time period from time t92 to time t93 is, for example,equal to or smaller than ⅓ the time period from time t92 to time t95.The time period from time t93 to time t94 is, for example, equal to orsmaller than ⅓ the time period from time t92 to time t95. The timeperiod from time t95 to time t96 is, for example, equal to or smallerthan ⅓ the time period from time t95 to time t98. The time period fromtime t96 to time t97 is, for example, equal to or smaller than ⅓ thetime period from time t95 to time t98.

This completes the description of the example of the shift in thevoltage of each signal in the transmission driver 152B. Next, a flow ofa series of processes of an electronic device (stylus 2 or touch sensormounted apparatus 3) including the transmission driver 152B will bedescribed in detail. FIG. 10 is a flow chart illustrating an example ofa flow of a series of processes of the electronic device including thetransmission driver 152B according to the second embodiment.

(Step SP40)

In the electronic device, the signal generation circuit 153B of thetransmission driver 152B determines whether or not the signal waveformof the input signal IN is rising. If the electronic device determinesthat the signal waveform of the input signal IN is rising, the processmoves to a process of step SP42. On the other hand, if the electronicdevice determines that the signal waveform of the input signal IN is notrising, the process moves to a process of step SP52.

(Step SP42)

The operation mode of the electronic device is the first mode. Theelectronic device causes the signal generation circuit 153B to shift thevoltage of the drive signal DRV from 0 V to the voltage VDD and outputsthe drive signal DRV to the output control circuit 154. The electronicdevice then causes the output control circuit 154 to shift the voltageof the transmission signal OUT from 0 V (first voltage) to the voltageVDD (second voltage). The process then moves to a process of step SP44.

(Step SP44)

The electronic device opens the short-circuit control element SW1 tostop the supply of the voltage VDD (second voltage) from the powersupply line W_VDD to the positive power supply terminal P of the outputcontrol circuit 154 and the other end of the capacitive element Cext1.The process then moves to a process of step SP46.

(Step SP46)

The electronic device switches the operation mode from the first mode tothe second mode. The electronic device causes the signal generationcircuit 153B to shift the voltage of the boost signal BST1 from 0 V tothe voltage VDD and outputs the boost signal BST1 to the buffer circuitBUF1. Accordingly, the voltage VP1 of the other end of the capacitiveelement Cext1 shifts from the voltage VDD (second voltage) to thevoltage (third voltage) that is twice the voltage VDD, and the voltage(third voltage) that is twice the voltage VDD is supplied to thepositive power supply terminal P of the output control circuit 154. As aresult, the electronic device causes the output control circuit 154 toshift the voltage of the transmission signal OUT from the voltage VDD(second voltage) to the voltage (third voltage) that is twice thevoltage VDD. The process then moves to a process of step SP48.

(Step SP48)

The electronic device opens the short-circuit control element SW2 tostop the supply of the voltage VDD from the power supply line W_VDD tothe power supply terminal of the buffer circuit BUF1 in the firstbooster circuit 155 and the other end of the capacitive element Cext2.The process then moves to a process of step SP50.

(Step SP50)

The electronic device switches the operation mode from the second modeto the third mode. In the electronic device in the third mode, thetransmission driver 152B transmits the transmission signal OUT with thevoltage in a range from 0 V (first voltage) to the voltage (sixthvoltage) higher than the voltage (third voltage) that is higher than thevoltage VDD (second voltage). The electronic device causes the signalgeneration circuit 153B to shift the voltage of the boost signal BST2from 0 V to the voltage VDD and outputs the boost signal BST2 to thebuffer circuit BUF2. Accordingly, the voltage VP2 of the other end ofthe capacitive element Cext2 shifts from the voltage VDD (seventhvoltage) to the voltage (eighth voltage) that is twice the voltage VDD,and the voltage (eighth voltage) that is twice the voltage VDD issupplied to the power supply terminal of the buffer circuit BUF1 in thefirst booster circuit 155. The voltage VP1 of the other end of thecapacitive element Cext1 shifts from the voltage (third voltage) that istwice the voltage VDD to the voltage (sixth voltage) that is three timesthe voltage VDD, and the voltage (sixth voltage) that is three times thevoltage VDD is supplied to the positive power supply terminal P in theoutput control circuit 154. As a result, the electronic device causesthe output control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage (third voltage) that is twice the voltageVDD to the voltage (sixth voltage) that is three times the voltage VDD.The process then moves to a process of step SP52.

(Step SP52)

In the electronic device, the signal generation circuit 153B of thetransmission driver 152B determines whether or not the signal waveformof the input signal IN is falling. If the electronic device determinesthat the signal waveform of the input signal IN is falling, the processmoves to a process of step SP54. On the other hand, if the electronicdevice determines that the signal waveform of the input signal IN is notfalling, the process ends the series of processes in FIG. 10 .

(Step SP54)

The electronic device switches the operation mode from the third mode tothe second mode. The electronic device causes the signal generationcircuit 153B to shift the voltage of the boost signal BST2 from thevoltage VDD to 0 V and outputs the boost signal BST2 to the buffercircuit BUF2. Accordingly, the voltage VP2 of the other end of thecapacitive element Cext2 shifts from the voltage (eighth voltage) thatis twice the voltage VDD to the voltage VDD (seventh voltage), and thevoltage VDD (seventh voltage) is supplied to the power supply terminalof the buffer circuit BUF1 in the first booster circuit 155. The voltageVP1 of the other end of the capacitive element Cext1 shifts from thevoltage (sixth voltage) that is three times the voltage VDD to thevoltage (third voltage) that is twice the voltage VDD, and the voltage(third voltage) that is twice the voltage VDD is supplied to thepositive power supply terminal P of the output control circuit 154. As aresult, the electronic device causes the output control circuit 154 toshift the voltage of the transmission signal OUT from the voltage (sixthvoltage) that is three times the voltage VDD to the voltage (thirdvoltage) that is twice the voltage VDD. The process then moves to aprocess of step SP56.

(Step SP56)

The electronic device switches the operation mode from the second modeto the first mode. The electronic device causes the signal generationcircuit 153B to shift the voltage of the boost signal BST1 from thevoltage VDD to 0 V and outputs the boost signal BST1 to the buffercircuit BUF1. Accordingly, the voltage VP1 of the other end of thecapacitive element Cext1 shifts from the voltage (third voltage) that istwice the voltage VDD to the voltage VDD (second voltage), and thevoltage VDD (second voltage) is supplied to the positive power supplyterminal P of the output control circuit 154. As a result, theelectronic device causes the output control circuit 154 to shift thevoltage of the transmission signal OUT from the voltage (third voltage)that is twice the voltage VDD to the voltage VDD (second voltage). Theprocess then moves to a process of step SP58.

(Step SP58)

The electronic device short-circuits the short-circuit control elementSW2 to supply the voltage VDD (seventh voltage) from the power supplyline W_VDD to the power supply terminal of the buffer circuit BUF1 inthe first booster circuit 155 and the other end of the capacitiveelement Cext2. The process then moves to a process of step SP60.

(Step SP60)

The electronic device causes the signal generation circuit 153B to shiftthe voltage of the drive signal DRV from the voltage VDD to 0 V andoutputs the drive signal DRV to the output control circuit 154. Theelectronic device then causes the output control circuit 154 to shiftthe voltage of the transmission signal OUT from the voltage VDD (secondvoltage) to 0 V (first voltage). The process then moves to a process ofstep SP62.

(Step SP62)

The electronic device short-circuits the short-circuit control elementSW1 to supply the voltage VDD (second voltage) from the power supplyline W_VDD to the positive power supply terminal P of the output controlcircuit 154 and the other end of the capacitive element Cext1.

Although the operation of the transmission driver 152B has beendescribed in the second embodiment by assuming that the capacitiveelements Cext1 and Cext2 in the transmission driver 152B havesubstantially the same capacitance, the configuration is not limited tothis. The capacitance of the capacitive element Cext1 and thecapacitance of the capacitive element Cext2 may be different in thetransmission driver 152B.

The sixth voltage is determined by the division ratio of the combinedcapacitance of the capacitive elements Cext1 and Cext2 to thecapacitance of the parasitic capacitance Cout or determined by thedivision ratio of the capacitance of the capacitive element Cext1 to thecapacitance of the parasitic capacitance Cout. Accordingly, the largerthe combined capacitance of the capacitive elements Cext1 and Cext2, thehigher the voltage. The power consumption can be reduced more, and thisis advantageous. Specifically, the relation between the sixth voltage,the combined capacitance of the capacitive elements Cext1 and Cext2, andthe parasitic capacitance Cout is expressed by the following equations 1to 5. Here, voltage V1 represents the second voltage (potential VDD).Voltage V2 represents the third voltage. voltage V3 represents the sixthvoltage. Voltage VA represents a voltage difference between the two endsof the capacitive element Cext1 in the second mode, that is, a voltagedifference between the third voltage (potential V2) and the secondvoltage (potential V1). Voltage VB represents a voltage differencebetween the two ends of the capacitive element Cext2 in the third mode,that is, a voltage difference (eighth voltage) between the sixth voltage(potential V3) and the second voltage (potential V2).

$\begin{matrix}\left\lbrack {{Math}.1} \right\rbrack &  \\{{V3} = {{V2} + {VB}}} & \left( {{equation}1} \right)\end{matrix}$ $\begin{matrix}\left\lbrack {{Math}.2} \right\rbrack &  \\{{V2} = {{VDD} + {VA}}} & \left( {{equation}2} \right)\end{matrix}$ $\begin{matrix}\left\lbrack {{Math}.3} \right\rbrack &  \\{{VB} = {\frac{{{Cext}1}//{{Cext}2}}{{{Cext}1}//{{{Cext}2} + {Cout}}} \times VDD}} & \left( {{equation}3} \right)\end{matrix}$ $\begin{matrix}\left\lbrack {{Math}.4} \right\rbrack &  \\{{VA} = {\frac{{Cext}1}{{{Cext}1} + {Cout}} \times VDD}} & \left( {{equation}4} \right)\end{matrix}$ $\begin{matrix}\left\lbrack {{Math}.5} \right\rbrack &  \\{{{{Cext}1}//{{Cext}2}} = \frac{{Cext}1 \times {Cext}2}{{{Cext}1} + {{Cext}2}}} & \left( {{equation}5} \right)\end{matrix}$

When the capacitive elements Cext1 and Cext2 are mounted on thetransmission driver 152B, the larger the capacitance of the capacitiveelements Cext1 and Cext2, the larger the area of the capacitive elementsCext1 and Cext2 on the transmission driver 152B. There is often an upperlimit to the area of the capacitive elements Cext1 and Cext2 on thetransmission driver 152B. Accordingly, there are combinations of thecapacitance of the capacitive element Cext1 and the capacitance of theCext2 that maximize the sixth voltage, based on the area of thecapacitive elements Cext1 and Cext2 when the capacitive elements Cext1and Cext2 are mounted on the transmission driver 152B. The relationbetween the combinations of the capacitance of the capacitive elementCext1 and the capacitance of the capacitive element Cext2 and the sixthvoltage will be described with reference to FIGS. 14 and 15 .

FIG. 14 is a chart illustrating an example of the relation between thecapacitance of the capacitive elements Cext1 and Cext2 and the voltageof the transmission signal OUT in the transmission driver 152B accordingto the second embodiment. FIG. 15 is a graph illustrating an example ofthe relation between a ratio C1norm of the capacitance of the capacitiveelement Cext1 to the capacitance of the capacitive element Cext2 and avoltage ratio V3norm of the transmission signal OUT in the transmissiondriver 152B according to the second embodiment. It is assumed in FIGS.14 and 15 that the total capacitance of the capacitive elements Cext1and Cext2 is 100 pF. It is also assumed in FIGS. 14 and 15 that thesecond voltage V1 is 11 V. It is also assumed in FIGS. 14 and 15 thatthe parasitic capacitance Cout is 10 pF.

FIG. 14 illustrates a ratio of the capacitance of the capacitive elementCext1 to the capacitance of the capacitive element Cext2 and values ofthe third voltage V2 and the sixth voltage V3 for each combination ofcapacitance when the capacitance of the capacitive element Cext1 and thecapacitance of the capacitive element Cext2 are changed at 5 pFintervals. FIG. 14 also illustrates, for each combination ofcapacitance, the ratio C1norm that is a ratio of the capacitance of thecapacitive element Cext1 to the total value of the capacitance of thecapacitive elements Cext1 and Cext2 and the voltage ratio V3norm that isa ratio of the sixth voltage V3 in one combination to the maximum valueof the sixth voltage V3 in the combinations.

As illustrated in FIGS. 14 and 15 , the sixth voltage V3 is equal to orgreater than 26.7 V when the ratio C1norm of the capacitance of thecapacitive element Cext1 to the capacitance of the capacitive elementCext2 is equal to or greater than 0.30 but smaller than 0.85. The valueof the voltage ratio V3norm is equal to or greater than 0.95. Note thatthe case in which the ratio C1norm of the capacitance of the capacitiveelement Cext1 to the capacitance of the capacitive element Cext2 isequal to or greater than 0.30 but smaller than 0.85 is a case in whichthe ratio of the capacitive element Cext1 to the capacitive elementCext2 is equal to or greater than 0.43 but smaller than 5.67 in otherwords. Moreover, when the ratio C1norm of the capacitance of thecapacitive element Cext1 to the capacitance of the capacitive elementCext2 is 0.60, the values of the sixth voltage V3 and the voltage ratioV3norm are maximum values, which are 28.19 V and 1.00, respectively. Thecase in which the ratio C1norm of capacitance is 0.60 is a case in whichthe ratio of the capacitive element Cext1 to the capacitive elementCext2 is 1.50. Accordingly, the value of the sixth voltage V3 becomeshigher when the ratio C1norm of the capacitance of the capacitiveelement Cext1 to the capacitance of the capacitive element Cext2 is setto be equal to or greater than 0.30 but smaller than 0.85. The value ofthe sixth voltage V3 is maximized when the ratio C1norm of thecapacitance of the capacitive element Cext1 to the capacitance of thecapacitive element Cext2 is set to 0.60.

Effects

In the second embodiment, the transmission driver 152B further includesthe third mode of transmitting the transmission signal OUT with thevoltage ranging from the voltage GND (first voltage) to the sixthvoltage higher than the third voltage.

According to the configuration, the transmission driver 152B can outputthe transmission signal OUT with the voltage (sixth voltage) even higherthan the supplied third voltage, and the voltage of the power supplythat supplies the voltage VDD can further be reduced. Thus, thetransmission driver 152B can independently reduce the power consumptionmore.

In the second embodiment, the transmission driver 152B further includesthe first booster circuit 155 that supplies the third voltage or thesixth voltage.

According to the configuration, the first booster circuit 155 in thetransmission driver 152B can supply the voltage (sixth voltage) evenhigher than the third voltage, and the voltage of the power supply thatsupplies the voltage VDD can further be reduced. Thus, the transmissiondriver 152B can independently reduce the power consumption more.

In the second embodiment, the transmission driver 152B further includesthe second booster circuit 156 that supplies, to the first boostercircuit 155, the seventh voltage higher than the voltage GND (firstvoltage) by the difference between the third voltage and the voltage VDD(second voltage) or the eighth voltage higher than the voltage GND bythe difference between the sixth voltage and the voltage VDD (secondvoltage).

According to the configuration, the second booster circuit 156 in thetransmission driver 152B supplies the voltage to the first boostercircuit 155. Thus, the transmission driver 152B can independently reducethe power consumption more with a simple configuration.

In the second embodiment, the first booster circuit 155 includes thefirst capacitive element Cext1 that supplies the third voltage V2 or thesixth voltage V3 from one end, the second booster circuit 156 includesthe second capacitive element Cext2 that supplies the seventh voltage orthe eighth voltage from one end to the first booster circuit 155, andthe capacitance of the first capacitive element Cext1 is 0.6 times thetotal capacitance of the first capacitive element Cext1 and the secondcapacitive element Cext2.

According to the configuration, the sixth voltage V3 becomes highervoltage in the transmission driver 152B. Thus, the transmission driver152B can independently reduce the power consumption more with a simpleconfiguration.

Third Embodiment

This completes the description of the second embodiment. Next, a thirdembodiment will be described.

Circuit Configuration

FIG. 11 depicts an example of a circuit configuration of a transmissiondriver 152C according to the third embodiment. As illustrated in FIG. 11, the transmission driver 152C includes, for example, a signalgeneration circuit 153C, the output control circuit 154, a third boostercircuit 157, short-circuit control elements SW1 to SW4, and a NOTcircuit INV3. Note that, in the description of the circuit configurationof the transmission driver 152C, the description of components similarto the components of the transmission driver 152A will appropriately beskipped.

The signal generation circuit 153C generates the drive signal DRV andthe boost signal BST1 according to the input signal IN that is input.The signal generation circuit 153C outputs the generated drive signalDRV to the NOT circuit INV3 and the output control circuit 154 andoutputs the generated boost signal BST1 to a buffer circuit BUF3 of thethird booster circuit 157. Specifically, the signal generation circuit153C generates the drive signal DRV such that the voltage is shiftedfrom the low level to the high level at the first timing and that thevoltage is shifted from the high level to the low level at the fourthtiming. The signal generation circuit 153C generates the boost signalBST1 such that the voltage is shifted from the low level to the highlevel at the second timing and that the voltage is shifted from the highlevel to the low level at the third timing.

The signal generation circuit 153C generates control signals CT3, CT5,and CT6 for controlling the short-circuit control elements SW1, SW3, andSW4. The signal generation circuit 153C uses the generated controlsignal CT3 to control the short-circuit control element SW1, uses thegenerated control signal CT5 to control the short-circuit controlelement SW3, and uses the generated control signal CT6 to control theshort-circuit control element SW4.

The NOT circuit INV3 is, for example, an inverter circuit including atransistor, and functions as a control circuit that uses a controlsignal CT4 to control the short-circuit control element SW2. The NOTcircuit INV3 performs a NOT operation of the drive signal DRV input fromthe signal generation circuit 153C, sets the signal that has beensubjected to the operation, as the control signal CT4, and outputs thecontrol signal CT4 to the control terminal of the short-circuit controlelement SW2.

The third booster circuit 157 includes, for example, the buffer circuitBUF3, capacitive elements Cext3 and Cext4, and output terminals RV1 andRV2. The third booster circuit 157 supplies ninth voltage that isvoltage between the low level (first voltage) and the voltage VDD(second voltage), tenth voltage that is voltage between the voltage VDD(second voltage) and the voltage (third voltage) that is twice thevoltage VDD, and the voltage (third voltage) that is twice the voltageVDD to the positive power supply terminal P of the output controlcircuit 154.

Specifically, when the voltage of the boost signal BST1 is in the lowlevel, the third booster circuit 157 divides voltage VP4 of a nodeconnected to the output terminal RV1 between the voltage VP4 and the lowlevel, to generate the voltage (ninth voltage) that is 0.5 times thevoltage VDD. When both ends of the short-circuit control element SW4 areshort-circuited, the third booster circuit 157 supplies the voltage(ninth voltage) that is 0.5 times the voltage VDD from the outputterminal RV2 to the positive power supply terminal P of the outputcontrol circuit 154 through the short-circuit control element SW4. Whenthe voltage of the boost signal BST1 output from the signal generationcircuit 153C is in the high level, the third booster circuit 157 booststhe voltage VP4 of the node connected to the output terminal RV1, togenerate the voltage (third voltage) that is twice the voltage VDD. Whenboth ends of the short-circuit control element SW3 are short-circuited,the third booster circuit 157 supplies the voltage (third voltage) thatis twice the voltage VDD from the output terminal RV1 to the positivepower supply terminal P of the output control circuit 154 through theshort-circuit control element SW3. When the voltage of the boost signalBST1 output from the signal generation circuit 153C is in the highlevel, the third booster circuit 157 divides the voltage VP4 of the nodeconnected to the output terminal RV1 between the voltage VP4 and thehigh level, to generate the voltage (tenth voltage) that is 1.5 timesthe voltage VDD. When both ends of the short-circuit control element SW4are short-circuited, the third booster circuit 157 supplies the voltage(tenth voltage) that is 1.5 times the voltage VDD from the outputterminal RV2 to the positive power supply terminal P of the outputcontrol circuit 154 through the short-circuit control element SW4.

The buffer circuit BUF3 is, for example, a buffer circuit including aMOS transistor. The buffer circuit BUF3 enhances the boost signal BST1output from the signal generation circuit 153C and outputs the enhancedboost signal BST1 to the capacitive element Cext3. The buffer circuitBUF3 reduces or eliminates the electrical effect that the capacitiveelement Cext3 and the signal generation circuit 153C exert on eachother. Although the buffer circuit BUF3 is provided on the transmissiondriver 152C in the third embodiment, the buffer circuit BUF3 may not beprovided, and the boost signal BST1 may directly be input from thesignal generation circuit 153C to one end of the capacitive elementCext3.

One end of the capacitive element Cext3 is connected to an outputterminal of the buffer circuit BUF3, and the other end of the capacitiveelement Cext3 is connected to one end of the capacitive element Cext4and the output terminal RV2. The capacitive element Cext3 suppliesvoltage VP3 from the output terminal RV2 to the positive power supplyterminal P of the output control circuit 154 through the short-circuitcontrol element SW4. The capacitance of the capacitive element Cext3 is,for example, 1 to 10 uF and is typically 1 uF.

One end of the capacitive element Cext4 is connected to the other end ofthe capacitive element Cext3 and the output terminal RV2, and the otherend of the capacitive element Cext4 is connected to the output terminalRV1. The capacitive element Cext4 supplies the voltage VP4 from theoutput terminal RV1 to the positive power supply terminal P of theoutput control circuit 154 through the short-circuit control elementSW3. The capacitance of the capacitive element Cext4 is, for example, 1to 10 uF and is typically 1 uF. The capacitance of the capacitiveelement Cext4 is, for example, equal to that of the capacitive elementCext3.

The short-circuit control elements SW1 to SW4 are, for example, switchelements or transistors. The short-circuit control elements SW1 to SW4short-circuit or open both ends according to control signals input tothe control terminals.

One end of the short-circuit control element SW1 is connected to thepower supply line W_VDD, and the other end of the short-circuit controlelement SW1 is connected to the other end of a short-circuit controlelement SW5, the other end of a short-circuit control element SW6, andthe positive power supply terminal P of the output control circuit 154.When the state of the control signal CT3 is the high state, theshort-circuit control element SW1 short-circuits both ends and suppliesthe voltage VDD of the power supply line W_VDD to the positive powersupply terminal P of the output control circuit 154. On the other hand,when the state of the control signal CT3 is the low state, theshort-circuit control element SW1 opens both ends and stops the supplyof the voltage VDD of the power supply line W_VDD.

One end of the short-circuit control element SW2 is connected to thepower supply line W_VDD, and the other end of the short-circuit controlelement SW2 is connected to the output terminal RV1 of the third boostercircuit 157 and one end of the short-circuit control element SW3. Whenthe state of the control signal CT4 is the high state, the short-circuitcontrol element SW2 short-circuits both ends and supplies the voltageVDD of the power supply line W_VDD to the output terminal RV1 of thethird booster circuit 157. On the other hand, when the state of thecontrol signal CT4 is the low state, the short-circuit control elementSW2 opens both ends and stops the supply of the voltage VDD of the powersupply line W_VDD.

One end of the short-circuit control element SW3 is connected to theother end of the short-circuit control element SW2 and the outputterminal RV1 of the third booster circuit 157, and the other end of theshort-circuit control element SW3 is connected to the other end of theshort-circuit control element SW1, the other end of the short-circuitcontrol element SW4, and the positive power supply terminal P of theoutput control circuit 154. When the state of the control signal CT5 isthe high state, the short-circuit control element SW3 short-circuitsboth ends and supplies the voltage VP4 of the output terminal RV1 of thethird booster circuit 157 to the positive power supply terminal P of theoutput control circuit 154. On the other hand, when the state of thecontrol signal CT5 is the low state, the short-circuit control elementSW3 opens both ends and stops the supply of the voltage VDD of the powersupply line W_VDD.

One end of the short-circuit control element SW4 is connected to theoutput terminal RV2 of the third booster circuit 157, and the other endof the short-circuit control element SW4 is connected to the other endof the short-circuit control element SW1, the other end of theshort-circuit control element SW5, and the positive power supplyterminal P of the output control circuit 154. When the state of thecontrol signal CT6 is the high state, the short-circuit control elementSW4 short-circuits both ends and supplies the voltage VP3 of the outputterminal RV2 to the output terminal RV1 of the third booster circuit157. On the other hand, when the state of the control signal CT6 is thelow state, the short-circuit control element SW4 opens both ends andstops the supply of the voltage VDD of the power supply line W_VDD.

In the transmission driver 152C configured in this way, the operationmode of the transmission driver 152C is the first mode while theshort-circuit control element SW1 is short-circuited, and the voltageVDD (second voltage) is supplied from the power supply line W_VDD to thepositive power supply terminal P of the output control circuit 154.

While the short-circuit control elements SW1, SW2, and SW4 are open butthe short-circuit control element SW3 is short-circuited, the operationmode of the transmission driver 152C is the second mode. Theshort-circuit control element SW1 cuts off the supply of the voltage VDDto the output control circuit 154, and the voltage VP4 is supplied fromthe output terminal RV1 of the third booster circuit 157 to the positivepower supply terminal P of the output control circuit 154 through theshort-circuit control element SW3. In the second mode, the voltage VP1is voltage equivalent to the sum of the voltage VP4 and the voltage ofone end of the capacitive element Cext3 determined by the boost signalBST1 corresponding to the input signal IN. Specifically, the voltage VP1is the voltage VDD (second voltage) when the voltage of one end of thecapacitive element Cext3 is the voltage GND, and the voltage VP1 is thevoltage (third voltage) that is twice the voltage VDD when the voltageof one end of the capacitive element Cext3 is the voltage VDD.

While the short-circuit control elements SW1 to SW3 are open but theshort-circuit control element SW4 is short-circuited, the short-circuitcontrol element SW1 cuts off the supply of the voltage VDD to the outputcontrol circuit 154, and the voltage VP3 is supplied from the outputterminal RV2 of the third booster circuit 157 to the positive powersupply terminal P of the output control circuit 154 through theshort-circuit control element SW4. While the short-circuit controlelements SW1 to SW3 are open but the short-circuit control element SW4is short-circuited, the voltage VP1 is voltage equivalent to the sum ofthe voltage VP3 and the voltage of one end of the capacitive elementCext3 determined by the boost signal BST1 corresponding to the inputsignal IN. Specifically, when the voltage of one end of the capacitiveelement Cext3 is the voltage GND, the operation mode of the transmissiondriver 152C is the fourth mode, and the voltage VP1 is the voltage(ninth voltage) that is 0.5 times the voltage VDD. On the other hand,when the voltage of one end of the capacitive element Cext3 is thevoltage VDD, the operation mode of the transmission driver 152C is afifth mode, and the voltage VP1 is the voltage (tenth voltage) that is1.5 times the voltage VDD.

The transmission driver 152C sets, as the transmission signal OUT, thevoltage supplied to the positive power supply terminal P of the outputcontrol circuit 154 or the voltage supplied to the negative power supplyterminal M of the output control circuit 154, according to the state ofthe input signal IN, and transmits the transmission signal OUT to theelectrode 20 or the linear electrode 32. That is, the transmissiondriver 152C generates the transmission signal OUT in which the voltageshifts to the voltage (ninth voltage) that is 0.5 times the voltage VDD,the voltage VDD (second voltage), the voltage (tenth voltage) that is1.5 times the voltage VDD, the voltage (third voltage) that is twice thevoltage VDD, and the voltage GND (first voltage), according to the inputsignal IN, and the transmission driver 152C transmits the transmissionsignal OUT to the electrode 20 or the linear electrode 32.

Flow of a Series of Operations Regarding Transmission Driver

This completes the description of the configuration of the transmissiondriver 152C. Next, the shift in the voltage of each signal in thetransmission driver 152C will be described in detail. FIG. 12 is atiming chart illustrating an example of the shift in the voltage of eachsignal in the transmission driver 152C according to the thirdembodiment.

At time t121, the operation mode of the transmission driver 152C is thefirst mode. At time t121, the driver selection circuit 151 or thecontroller 28 shifts the voltage of the input signal IN from 0 V to thevoltage VDD. At time t121, the signal generation circuit 153C detects arise in the voltage of the input signal IN. At time t121, theshort-circuit control element SW2 is short-circuited, and the voltageVDD is supplied from the power supply line W_VDD to the other end of thecapacitive element Cext4 through the output terminal RV1 of the thirdbooster circuit 157. At time t121, the short-circuit control elementsSW1, SW3, and SW4 are open. Accordingly, the voltage of the voltage VP4is the voltage VDD (second voltage) at time t121. At time t121, thesignal generation circuit 153C sets the voltage of the boost signal BST1to 0 V and outputs the boost signal BST1 to the buffer circuit BUF3. Inassociation with this, the third booster circuit 157 supplies thevoltage of 0 V to one end of the capacitive element Cext3. At time t121,the voltage VP3 is the voltage (ninth voltage) that is 0.5 times thevoltage VDD. At time t121, the output control circuit 154 sets thevoltage of the transmission signal OUT to 0 V (first voltage) andtransmits the transmission signal OUT to the electrode 20 or the linearelectrode 32.

At time t122, the operation mode of the transmission driver 152C isswitched from the first mode to the fourth mode. At time t122, thesignal generation circuit 153C shifts the voltage of the drive signalDRV from 0 V to the voltage VDD according to a rise of the input signalIN. At time t122, the NOT circuit INV3 shifts the voltage of the controlsignal CT4 from the voltage VDD to 0 V. At time t122, both ends of theshort-circuit control element SW2 are opened according to the controlsignal CT4 in which the voltage is 0 V. At time t122, the supply of thevoltage VDD (second voltage) from the power supply line W_VDD to theother end of the capacitive element Cext4 through the output terminalRV1 of the third booster circuit 157 stops. At time t122, the signalgeneration circuit 153C shifts the voltage of the control signal CT6from 0 V to the voltage VDD. At time t122, both ends of theshort-circuit control element SW4 are short-circuited according to thecontrol signal CT6 in which the voltage is the voltage VDD. Inassociation with this, the third booster circuit 157 supplies thevoltage VP3 from the output terminal RV2 to the positive power supplyterminal P of the output control circuit 154 through the short-circuitcontrol element SW4 at time t122. Accordingly, at time t122, the voltageof the voltage VP1 is the voltage (ninth voltage) that is 0.5 times thevoltage VDD. At time t122, the output control circuit 154 shifts thevoltage of the transmission signal OUT from 0 V (first voltage) to thevoltage (ninth voltage) that is 0.5 times the voltage VDD supplied tothe positive power supply terminal P, according to the drive signal DRV.

At time t123, the operation mode of the transmission driver 152C isswitched from the fourth mode to the first mode. At time t123, thesignal generation circuit 153C shifts the voltage of the control signalCT3 from 0 V to the voltage VDD and shifts the voltage of the controlsignal CT6 from the voltage VDD to 0 V. At time t123, both ends of theshort-circuit control element SW4 are opened according to the controlsignal CT6 in which the voltage is 0 V. At time t123, both ends of theshort-circuit control element SW1 are short-circuited according to thecontrol signal CT3 in which the voltage is the voltage VDD. Inassociation with this, the supply of the voltage VP3 (ninth voltage:voltage 0.5 times the voltage VDD) from the output terminal RV2 of thethird booster circuit 157 to the positive power supply terminal P of theoutput control circuit 154 through the short-circuit control element SW4stops at time t123. At time t123, the voltage VDD is supplied from thepower supply line W_VDD to the positive power supply terminal P of theoutput control circuit 154 through the short-circuit control elementSW1. Accordingly, at time t123, the voltage of the voltage VP1 is thevoltage VDD (second voltage). At time t123, the output control circuit154 shifts the voltage of the transmission signal OUT from the voltage(ninth voltage) that is 0.5 times the voltage VDD to the voltage VDD(second voltage).

At time t124, the operation mode of the transmission driver 152C isswitched from the first mode to the fifth mode. At time t124, the signalgeneration circuit 153C shifts the voltage of the control signal CT3from the voltage VDD to 0 V, shifts the voltage of the control signalCT6 from 0 V to the voltage VDD, and shifts the voltage of the boostsignal BST1 from 0 V to the voltage VDD. At time t124, both ends of theshort-circuit control element SW1 are opened according to the controlsignal CT3 in which the voltage is 0 V. At time t124, the supply of thevoltage VDD (second voltage) from the power supply line W_VDD to thepositive power supply terminal P of the output control circuit 154through the short-circuit control element SW1 stops. At time t124, thethird booster circuit 157 supplies the voltage of the voltage VDD to oneend of the capacitive element Cext3. In association with this, thecapacitive elements Cext3 and Cext4 try to hold the voltage differencebetween the two ends, and the voltage VP4 of the other end of thecapacitive element Cext4 shifts from the voltage VDD to the voltage(third voltage: 2×voltage VDD) equivalent to the sum of the voltage VDDand the voltage (potential VDD) of one end of the capacitive elementCext3, at time t124. The voltage VP3 of the other end of the capacitiveelement Cext3 shifts from the voltage 0.5 times the voltage VDD to thevoltage (tenth voltage: 1.5×voltage VDD) equivalent to the sum of thevoltage VDD and the voltage (potential VDD) of one end of the capacitiveelement Cext3. At time t124, both ends of the short-circuit controlelement SW4 are short-circuited according to the control signal CT6 inwhich the voltage is the voltage VDD. In association with this, thethird booster circuit 157 supplies the voltage VP3 from the outputterminal RV2 to the positive power supply terminal P of the outputcontrol circuit 154 through the short-circuit control element SW4 attime t124. Accordingly, at time t124, the voltage of the voltage VP1 isthe voltage (tenth voltage) that is 1.5 times the voltage VDD. At timet124, the output control circuit 154 shifts the voltage of thetransmission signal OUT from the voltage VDD (second voltage) to thevoltage (tenth voltage) that is 1.5 times the voltage VDD.

At time t125, the operation mode of the transmission driver 152C isswitched from the fifth mode to the second mode. At time t125, thesignal generation circuit 153C shifts the voltage of the control signalCT6 from the voltage VDD to 0 V and shifts the voltage of the controlsignal CT5 from 0 V to the voltage VDD. At time t125, both ends of theshort-circuit control elements SW4 are opened according to the controlsignal CT6 in which the voltage is 0 V. At time t125, the supply of thevoltage VP3 from the output terminal RV2 of the third booster circuit157 to the positive power supply terminal P of the output controlcircuit 154 through the short-circuit control element SW4 stops. At timet125, both ends of the short-circuit control element SW3 areshort-circuited according to the control signal CT5 in which the voltageis the voltage VDD. In association with this, the third booster circuit157 supplies the voltage VP4 from the output terminal RV1 to thepositive power supply terminal P of the output control circuit 154through the short-circuit control element SW3 at time t125. Accordingly,at time t125, the voltage of the voltage VP1 is the voltage (thirdvoltage) that is twice the voltage VDD. At time t125, the output controlcircuit 154 shifts the voltage of the transmission signal OUT from thevoltage (tenth voltage) that is 1.5 times the voltage VDD to the voltage(third voltage) that is twice the voltage VDD.

At time t126, the driver selection circuit 151 or the controller 28shifts the voltage of the input signal IN from the voltage VDD to 0 V.At time t126, the signal generation circuit 153C detects a fall in thevoltage of the input signal IN. At time t126, the output control circuit154 keeps the voltage of the transmission signal OUT set to the voltageVP1 (third voltage: 2×voltage VDD) and transmits the transmission signalOUT to the electrode 20 or the linear electrode 32.

At time t127, the operation mode of the transmission driver 152C isswitched from the second mode to the fifth mode. At time t127, thesignal generation circuit 153C shifts the voltage of the control signalCT6 from 0 V to the voltage VDD and shifts the voltage of the controlsignal CT5 from the voltage VDD to 0 V. At time t127, both ends of theshort-circuit control element SW3 are opened according to the controlsignal CT5 in which the voltage is 0 V. At time t127, the supply of thevoltage VP4 (third voltage: voltage twice the voltage VDD) from theoutput terminal RV1 of the third booster circuit 157 to the positivepower supply terminal P of the output control circuit 154 through theshort-circuit control element SW3 stops. At time t127, both ends of theshort-circuit control element SW4 are short-circuited according to thecontrol signal CT6 in which the voltage is the voltage VDD. Inassociation with this, the third booster circuit 157 supplies thevoltage VP3 from the output terminal RV2 to the positive power supplyterminal P of the output control circuit 154 through the short-circuitcontrol element SW4 at time t127. Accordingly, at time t127, the voltageof the voltage VP1 is the voltage (tenth voltage) 1.5 times the voltageVDD at time t127. At time t127, the output control circuit 154 shiftsthe voltage of the transmission signal OUT from the voltage (thirdvoltage) twice the voltage VDD to the voltage (tenth voltage) 1.5 timesthe voltage VDD.

At time t128, the operation mode of the transmission driver 152C isswitched from the fifth mode to the first mode. At time t128, the signalgeneration circuit 153C shifts the voltage of the control signal CT3from 0 V to the voltage VDD, shifts the voltage of the control signalCT6 from the voltage VDD to 0 V, and shifts the voltage of the boostsignal BST1 from the voltage VDD to 0 V. At time t128, both ends of theshort-circuit control element SW4 are opened according to the controlsignal CT6 in which the voltage is 0 V. At t128, both ends of theshort-circuit control element SW1 are short-circuited according to thecontrol signal CT3 in which the voltage is the voltage VDD. Inassociation with this, the capacitive elements Cext3 and Cext4 try tohold the voltage difference between the two ends, and the voltage VP4 ofthe other end of the capacitive element Cext4 shifts from the voltage(third voltage) that is twice the voltage VDD to the voltage VDD (secondvoltage) at time t128. The voltage VP3 of the other end of thecapacitive element Cext3 shifts from the voltage (tenth voltage) that is1.5 times the voltage VDD to the voltage (ninth voltage) that is 0.5times the voltage VDD. At time t128, the supply of the voltage VP3(ninth voltage: voltage 0.5 times the voltage VDD) from the outputterminal RV2 of the third booster circuit 157 to the positive powersupply terminal P of the output control circuit 154 through theshort-circuit control element SW4 stops. At time t128, the voltage VDDis supplied from the power supply line W_VDD to the positive powersupply terminal P of the output control circuit 154 through theshort-circuit control element SW1. Accordingly, at time t128, thevoltage of the voltage VP1 is the voltage VDD (second voltage). At timet128, the output control circuit 154 shifts the voltage of thetransmission signal OUT from the voltage (tenth voltage) that is 1.5times the voltage VDD to the voltage VDD (second voltage).

At time t129, the operation mode of the transmission driver 152C isswitched from the first mode to the fourth mode. At time t129, thesignal generation circuit 153C shifts the voltage of the control signalCT6 from OV to the voltage VDD and shifts the voltage of the controlsignal CT3 from the voltage VDD to 0 V. At time t129, both ends of theshort-circuit control element SW1 are opened according to the controlsignal CT3 in which the voltage is 0 V. In association with this, thesupply of the voltage VDD (second voltage) from the power supply lineW_VDD to the positive power supply terminal P of the output controlcircuit 154 through the short-circuit control element SW1 stops at timet129. At time t129, both ends of the short-circuit control element SW4are short-circuited according to the control signal CT6 in which thevoltage is the voltage VDD. In association with this, the third boostercircuit 157 supplies the voltage VP3 from the output terminal RV2 of thethird booster circuit 157 to the positive power supply terminal P of theoutput control circuit 154 through the short-circuit control element SW4at time t129. Accordingly, at time t129, the voltage of the voltage VP1is the voltage (ninth voltage) that is 0.5 times the voltage VDD. Attime t129, the output control circuit 154 shifts the voltage of thetransmission signal OUT from the voltage VDD (second voltage) to thevoltage (ninth voltage) that is 0.5 times the voltage VDD.

At time t130, the operation mode of the transmission driver 152C isswitched from the fourth mode to the first mode. At time t130, thesignal generation circuit 153C shifts the voltage of the drive signalDRV from the voltage VDD to 0 V according to a fall of the input signalIN. At time t130, the NOT circuit INV3 shifts the voltage of the controlsignal CT4 from 0 V to the voltage VDD. At time t130, both ends of theshort-circuit control element SW2 are short-circuited according to thecontrol signal CT4 in which the voltage is the voltage VDD. At timet130, the voltage VDD (second voltage) is supplied from the power supplyline W_VDD to the other end of the capacitive element Cext2 through theshort-circuit control element SW2. At time t130, the output controlcircuit 154 shifts the voltage of the transmission signal OUT from thevoltage (ninth voltage) that is 0.5 times the voltage VDD to 0 V (firstvoltage) supplied to the negative power supply terminal M, according tothe drive signal DRV.

Note that the time period from time t122 to time t123, the time periodfrom time t123 to time t124, and the time period from time t124 to timet125 are, for example, equal to or smaller than ¼ the time period fromtime t122 to time t126. The time period from time t127 to time t128, thetime period from time t128 to time t129, and the time period from timet129 to time t130 are, for example, equal to or smaller than ¼ the timeperiod from time t126 to time t130.

This completes the description of the example of the shift in thevoltage of each signal in the transmission driver 152C. Next, a flow ofa series of processes of an electronic device (stylus 2 or touch sensormounted apparatus 3) including the transmission driver 152C will bedescribed in detail. FIG. 13 is a flow chart illustrating an example ofa flow of a series of processes of the electronic device including thetransmission driver 152C according to the third embodiment.

(Step SP80)

In the electronic device, the signal generation circuit 153C of thetransmission driver 152C determines whether or not the signal waveformof the input signal IN is rising. If the electronic device determinesthat the signal waveform of the input signal IN is rising, the processmoves to a process of step SP82. On the other hand, if the electronicdevice determines that the signal waveform of the input signal IN is notrising, the process moves to a process of step SP94.

(Step SP82)

The operation mode of the electronic device is the first mode. In theelectronic device, the transmission driver 152C transmits thetransmission signal OUT with the voltage of 0 V (first voltage). Theelectronic device causes the signal generation circuit 153C to shift thevoltage of the drive signal DRV from 0 V to the voltage VDD and outputsthe drive signal DRV to the output control circuit 154. The electronicdevice opens the short-circuit control element SW2 to stop the supply ofthe voltage VDD (second voltage) from the power supply line W_VDD to theother end of the capacitive element Cext4. The short-circuit controlelements SW1, SW3, and SW4 are open in the electronic device. In theelectronic device, the third booster circuit 157 generates the voltage(ninth voltage) that is 0.5 times the voltage VDD. The process thenmoves to a process of step SP84.

(Step SP84)

The electronic device switches the operation mode from the first mode tothe fourth mode. In the electronic device in the fourth mode, thetransmission driver 152C transmits the transmission signal OUT with thevoltage in a range from 0 V (first voltage) to the voltage (ninthvoltage) between 0 V (first voltage) and the voltage VDD (secondvoltage). The electronic device short-circuits the short-circuit controlelement SW4 to supply the voltage (ninth voltage) that is 0.5 times thevoltage VDD from the output terminal RV2 of the third booster circuit157 to the positive power supply terminal P of the output controlcircuit 154. As a result, the electronic device causes the outputcontrol circuit 154 to shift the voltage of the transmission signal OUTfrom 0 V (first voltage) to the voltage (ninth voltage) that is 0.5times the voltage VDD. The process then moves to a process of step SP86.

(Step SP86)

The electronic device switches the operation mode from the fourth modeto the first mode. The electronic device opens the short-circuit controlelement SW4 to stop the supply of the voltage (ninth voltage) that is0.5 times the voltage VDD from the output terminal RV2 of the thirdbooster circuit 157 to the positive power supply terminal P of theoutput control circuit 154. The electronic device short-circuits theshort-circuit control element SW1 to supply the voltage VDD (secondvoltage) from the power supply line W_VDD to the positive power supplyterminal P of the output control circuit 154. As a result, theelectronic device causes the output control circuit 154 to shift thevoltage of the transmission signal OUT from the voltage (ninth voltage)that is 0.5 times the voltage VDD to the voltage VDD (second voltage).The process then moves to a process of step SP88.

(Step SP88)

The electronic device switches the operation mode from the first mode tothe fifth mode. In the electronic device in the fifth mode, thetransmission driver 152C transmits the transmission signal OUT with thevoltage in a range from the voltage VDD (second voltage) to the voltage(tenth voltage) that is between the voltage (third voltage) higher thanthe voltage VDD (second voltage) and the voltage VDD (second voltage).The electronic device causes the signal generation circuit 153C to shiftthe voltage of the boost signal BST1 from 0 V to the voltage VDD andoutputs the boost signal BST1 to the buffer circuit BUF3. In associationwith this, the voltage VP4 of the other end of the capacitive elementCext4 shifts from the voltage VDD (second voltage) to the voltage (thirdvoltage) that is twice the voltage VDD. The voltage VP3 of the other endof the capacitive element Cext3 shifts from the voltage (ninth voltage)that is 0.5 times the voltage VDD to the voltage (tenth voltage) that is1.5 times the voltage VDD. The process then moves to a process of stepSP90.

(Step SP90)

The electronic device opens the short-circuit control element SW1 tostop the supply of the voltage VDD (second voltage) from the powersupply line W_VDD to the positive power supply terminal P of the outputcontrol circuit 154. The electronic device short-circuits theshort-circuit control element SW4 to supply the voltage (tenth voltage)that is 1.5 times the voltage VDD from the output terminal RV2 of thethird booster circuit 157 to the positive power supply terminal P of theoutput control circuit 154. As a result, the electronic device causesthe output control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage VDD (second voltage) to the voltage (tenthvoltage) that is 1.5 times the voltage VDD. The process then moves to aprocess of step SP92.

(Step SP92)

The electronic device switches the operation mode from the fifth mode tothe second mode. The electronic device opens the short-circuit controlelement SW4 to stop the supply of the voltage (tenth voltage) 1.5 timesthe voltage VDD from the output terminal RV2 of the third boostercircuit 157 to the positive power supply terminal P of the outputcontrol circuit 154. The electronic device short-circuits theshort-circuit control element SW3 to supply the voltage (third voltage)twice the voltage VDD from the output terminal RV1 of the third boostercircuit 157 to the positive power supply terminal P of the outputcontrol circuit 154. As a result, the electronic device causes theoutput control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage (tenth voltage) that is 1.5 times thevoltage VDD to the voltage (third voltage) that is twice the voltageVDD. The process then moves to a process of step SP94.

(Step SP94)

In the electronic device, the signal generation circuit 153C of thetransmission driver 152C determines whether or not the signal waveformof the input signal IN is falling. If the electronic device determinesthat the signal waveform of the input signal IN is falling, the processmoves to a process of step SP96. On the other hand, if the electronicdevice determines that the signal waveform of the input signal IN is notfalling, the process ends the series of processes in FIG. 13 .

(Step SP96)

The operation mode is switched from the second mode to the fifth mode.The electronic device causes the signal generation circuit 153C to shiftthe voltage of the drive signal DRV from the voltage VDD to 0 V andoutputs the drive signal DRV to the output control circuit 154. Theelectronic device opens the short-circuit control element SW3 to stopthe supply of the voltage (third voltage) that is twice the voltage VDDfrom the output terminal RV1 of the third booster circuit 157 to thepositive power supply terminal P of the output control circuit 154. Theelectronic device short-circuits the short-circuit control element SW4to supply the voltage (tenth voltage) that is 1.5 times the voltage VDDfrom the output terminal RV2 of the third booster circuit 157 to thepositive power supply terminal P of the output control circuit 154. Theprocess then moves to a process of step SP98.

(Step SP98)

The electronic device switches the operation mode from the fifth mode tothe first mode. The electronic device causes the signal generationcircuit 153C to shift the voltage of the boost signal BST1 from thevoltage VDD to 0 V and outputs the boost signal BST1 to the buffercircuit BUF3. In association with this, the voltage VP4 of the other endof the capacitive element Cext4 shifts from the voltage (third voltage)that is twice the voltage VDD to the voltage VDD (second voltage). Thevoltage VP3 of the other end of the capacitive element Cext3 shifts fromthe voltage (tenth voltage) that is 1.5 times the voltage VDD to thevoltage (ninth voltage) that is 0.5 times the voltage VDD. The processthen moves to a process of step SP100.

(Step SP100)

The electronic device opens the short-circuit control element SW4 tostop the supply of the voltage (tenth voltage) that is 1.5 times thevoltage VDD from the output terminal RV2 of the third booster circuit157 to the positive power supply terminal P of the output controlcircuit 154. The electronic device short-circuits the short-circuitcontrol element SW1 to supply the voltage VDD (second voltage) from thepower supply line W_VDD to the positive power supply terminal P of theoutput control circuit 154. As a result, the electronic device causesthe output control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage (tenth voltage) that is 1.5 times thevoltage VDD to the voltage VDD (second voltage). The process then movesto a process of step SP102.

(Step SP102)

The electronic device switches the operation mode from the first mode tothe fourth mode. The electronic device opens the short-circuit controlelement SW1 to stop the supply of the voltage VDD (second voltage) fromthe power supply line W_VDD to the positive power supply terminal P ofthe output control circuit 154. The electronic device short-circuits theshort-circuit control element SW4 to supply the voltage (ninth voltage)0.5 times the voltage VDD from the output terminal RV2 of the thirdbooster circuit 157 to the positive power supply terminal P of theoutput control circuit 154. As a result, the electronic device causesthe output control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage VDD (second voltage) to the voltage (ninthvoltage) that is 0.5 times the voltage VDD. The process then moves to aprocess of step SP104.

(Step SP104)

The electronic device switches the operation mode from the fourth modeto the first mode. The electronic device opens the short-circuit controlelement SW4 to stop the supply of the voltage (ninth voltage) 0.5 timesthe voltage VDD from the output terminal RV2 of the third boostercircuit 157 to the positive power supply terminal P of the outputcontrol circuit 154. The electronic device causes the signal generationcircuit 153C to shift the voltage of the drive signal DRV from thevoltage VDD to 0 V and outputs the drive signal DRV to the outputcontrol circuit 154. As a result, the electronic device causes theoutput control circuit 154 to shift the voltage of the transmissionsignal OUT from the voltage (ninth voltage) that is 0.5 times thevoltage VDD and that is supplied to the positive power supply terminal Pto 0 V (first voltage) supplied to the negative power supply terminal M.

Effects

In the third embodiment, the transmission driver 152C further includesthe fourth mode of transmitting the transmission signal OUT with thevoltage ranging from the voltage GND (first voltage) to the ninthvoltage that is voltage between the voltage GND (first voltage) and thevoltage VDD (second voltage) and the fifth mode of transmitting thetransmission signal OUT with the voltage ranging from the voltage GND(first voltage) to the tenth voltage that is voltage between the voltageVDD (second voltage) and the third voltage.

According to the configuration, the transmission driver 152C can morefinely control the voltage of the transmission signal OUT between thevoltage GND (first voltage) and the third voltage.

In the third embodiment, the transmission driver 152C further includesthe third booster circuit 157 that supplies the ninth voltage, the tenthvoltage, or the third voltage.

According to the configuration, the third booster circuit 157 in thetransmission driver 152C can supply the ninth voltage, the tenthvoltage, and the third voltage, and the transmission driver 152C canmore finely control the voltage of the transmission signal OUT.

In the third embodiment, the third booster circuit 157 divides thevoltage GND (first voltage) and the voltage VDD (second voltage) togenerate the ninth voltage and boosts the generated ninth voltage by theamount of the voltage VDD (second voltage) to generate the tenthvoltage.

According to the configuration, the transmission driver 152C can morefinely control the voltage of the transmission signal OUT between thevoltage GND (first voltage) and the third voltage with a simpleconfiguration.

In the third embodiment, the third booster circuit 157 includes at leastone or more capacitive elements Cext3 and Cext4, and the capacitiveelements Cext3 and Cext4 supply charge or receive charge according tothe shift in the voltage of the transmission signal OUT.

According to the configuration, the third booster circuit 157 in thetransmission driver 152C includes the capacitive elements Cext3 andCext4. The capacitive elements Cext3 and Cext4 supply charge, or chargeis supplied to the capacitive elements Cext3 and Cext4, according to theshift in the voltage of the transmission signal OUT. Thus, thetransmission driver 152C can independently reduce the power consumptionmore than the transmission driver 152A in the first embodiment.

Modifications

Note that the present disclosure is not limited to the embodiments. Thatis, those skilled in the art can appropriately change the design of theembodiments, and the changed embodiments are also included in the scopeof the present disclosure as long as the changed embodiments have thefeatures of the present disclosure. In addition, the elements includedin the embodiments and modifications described later can be combined iftechnically possible, and the combinations are also included in thescope of the present disclosure as long as the combinations have thefeatures of the present disclosure.

For example, although the signal generation circuits 153A and 153C setthe high levels of the drive signal DRV and the boost signal BST1 to thevoltage VDD (fourth voltage) and the voltage VDD (fifth voltage) andgenerate the signals such that the high levels have the same voltage inthe first and third embodiments, the configuration is not limited tothis. That is, the signal generation circuits 153A and 153C may generatethe signals such that the high level (fourth voltage) of the drivesignal DRV and the high level (fifth voltage) of the boost signal BST1are different.

According to the configuration, the transmission drivers 152A and 152Ccan independently realize the reduction in power consumption even whenthere are two or more power supply systems. In addition, thetransmission driver 152A can set the voltage of the transmission signalOUT to voltage equivalent to the sum of the high level (fifth voltage)of the boost signal BST1 and the voltage VDD (second voltage) of thepower supply line W_VDD and output the transmission signal OUT. That is,the transmission driver 152A can adjust the high level (fifth voltage)of the boost signal BST1 to adjust the voltage (third voltage) todesirable voltage when the voltage of the transmission signal OUT isvoltage exceeding the voltage VDD (second voltage). In addition, thetransmission driver 152C can set the voltage of the transmission signalOUT to voltage equivalent to the sum of the high level of the boostsignal BST1 and one of the voltage VDD (second voltage) and the voltage(ninth voltage) that is 0.5 times the voltage VDD and output thetransmission signal OUT. That is, the transmission driver 152C canadjust the high level of the boost signal BST1 to adjust the voltage ofthe transmission signal OUT to desirable voltage.

Although the signal generation circuit 153B generates the drive signalDRV and the boost signals BST1 and BST2 such that the high levels of thesignals have the same voltage in the second embodiment, theconfiguration is not limited to this. That is, the signal generationcircuit 153B may generate the signals such that the high level of thedrive signal DRV, the high level of the boost signal BST1, and the highlevel of the boost signal BST2 are different.

According to the configuration, the transmission driver 152B canindependently realize the reduction in power consumption even when thereare three or more power supply systems.

Although the signal generation circuit 153C generates the drive signalDRV and the boost signals BST1 and BST2 such that the high levels of thesignals have the same voltage in the third embodiment, the configurationis not limited to this. That is, the signal generation circuit 153C maygenerate the signals such that the high level of the drive signal DRV,the high level of the boost signal BST1, and the high level of the boostsignal BST2 are different.

According to the configuration, the transmission driver 152C canindependently realize the reduction in power consumption even when thereare three or more power supply systems.

Although one of the signal generation circuits 153A to 153C generatesthe drive signal DRV and the boost signals BST1 and BST2 according tothe input signal IN in the first to third embodiments, the configurationis not limited to this. For example, when a shift in voltage of theinput signal IN is known in advance, a boost signal generation circuitthat generates at least one of the boost signals BST1 and BST2 accordingto the pattern of the shift in voltage of the input signal IN maygenerate at least one of the boost signals BST1 and BST2. In this case,the input signal IN may directly be used for the drive signal DRV.

According to the configuration, the delay time from the input of theinput signal IN into the transmission drivers 152A to 152C to thetransmission of the transmission signal OUT can be reduced.

Although the transmission drivers 152A to 152C use the NOT circuits INV1to INV3 as control circuits that generate one of the control signalsCT1, CT2, and CT4 for controlling the short-circuit control elements SW1and SW2 in the first to third embodiments, the configuration is notlimited to this. The transmission drivers 152A to 152C may use, in placeof the NOT circuits INV1 to INV3, control circuits that generate one ofthe control signals CT1, CT2, and CT4 according to the input signal INor may use control circuits that generate one of the control signalsCT1, CT2, and CT4 according to the pattern of shift in the voltage ofthe input signal IN known in advance, for example.

Although the transmission drivers 152A to 152C are mounted on the stylus2 or the touch sensor mounted apparatus 3 in the first to thirdembodiments, the configuration is not limited to this. The transmissiondrivers 152A to 152C may be mounted on any electronic device that mayneed to have a function of outputting the transmission signal OUT withvoltage higher than the voltage of the power supply system according tothe input signal IN.

Although the transmission driver 152B includes two booster circuits thatare the first booster circuit 155 and the second booster circuit 156 inthe second embodiment, the configuration is not limited to this. Thetransmission driver 152B may include three or more booster circuits andshort-circuit control elements, each short-circuit control element beingassociated with each booster circuit and configured to control openingand short-circuiting of the current path between the output terminal ofthe associated booster circuit and the power supply line W_VDD. In thetransmission driver 152B in this case, each booster circuit other thanthe first booster circuit 155 receives boosted voltage from the boostercircuit of the former stage through the power supply terminal orreceives the voltage VDD from the power supply line W_VDD through thecorresponding short-circuit control element.

According to the configuration, the larger the number of providedbooster circuits is, the more the transmission driver 152B canindependently reduce the power consumption.

Although the third booster circuit 157 includes two capacitive elementsCext3 and Cext4 in the third embodiment, the configuration is notlimited to this. The third booster circuit 157 may include three or morecapacitive elements connected in series. In the third booster circuit157, the capacitive elements connected in series divide the voltagesupplied to the output terminal RV1 and the voltage of the outputterminal of the buffer circuit BUF3, and the divided different voltageis supplied from each connection part of the capacitive elementsconnected in series. The signal generation circuit 153C controls theshort-circuit control elements and the voltage of the boost signal BST1to supply, in ascending order or descending order, the values of thevoltage supplied from the third booster circuit 157 and the voltagesupplied from the power supply line W_VDD through the short-circuitcontrol element SW1, to the positive power supply terminal P of theoutput control circuit 154.

According to the configuration, the larger the number of capacitiveelements provided on the third booster circuit 157 is, the more thetransmission driver 152C can independently reduce the power consumption.

The various embodiments described above can be combined to providefurther embodiments. Aspects of the embodiments can be modified, ifnecessary to employ concepts of the various patents, applications andpublications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A transmission driver that receives an input signal, a first voltage,and a second voltage higher than the first voltage and that transmits atransmission signal according to the input signal, the transmissiondriver comprising: an output terminal which, in operation, outputs thetransmission signal; and circuitry coupled to the output terminal,wherein the circuitry, in operation, operates in: a first mode oftransmitting the transmission signal with a first voltage range thatranges from the first voltage to the second voltage; and a second modeof transmitting the transmission signal with a second voltage range thatranges from the first voltage to a third voltage higher than the secondvoltage.
 2. The transmission driver according to claim 1, furthercomprising: a first booster circuit which, in operation, supplies thethird voltage.
 3. The transmission driver according to claim 2, furthercomprising: an output control circuit which, in operation, receives thefirst voltage and one of the second voltage and the third voltage andoutputs the transmission signal from the output terminal; and ashort-circuit control element which, in operation, controls supply ofthe second voltage to the output control circuit.
 4. The transmissiondriver according to claim 3, wherein the first booster circuit includesa capacitive element.
 5. The transmission driver according to claim 4,wherein, in the first mode, the second voltage is supplied to the outputcontrol circuit through the short-circuit control element, and in thesecond mode, the short-circuit control element cuts off the supply ofthe second voltage to the output control circuit, and the first boostercircuit supplies the third voltage to the output control circuit.
 6. Thetransmission driver according to claim 5, wherein the output controlcircuit includes a positive power supply terminal and a negative powersupply terminal, the first voltage is supplied to the negative powersupply terminal, the second voltage is supplied to a first end of theshort-circuit control element, and a second end of the short-circuitcontrol element and a first end of the capacitive element are connectedto the positive power supply terminal.
 7. The transmission driveraccording to claim 6, further comprising: a signal generation circuitwhich, in operation, generates a first signal and a second signalaccording to the input signal, wherein: the output control circuit sets,as the transmission signal, a first supplied voltage that is supplied tothe positive power supply terminal or a second supplied voltage that issupplied to the negative power supply terminal, according to the firstsignal, and outputs the transmission signal, and the second signal isinput to a second end of the capacitive element.
 8. The transmissiondriver according to claim 7, further comprising: a control circuitwhich, in operation, controls the short-circuit control element toshort-circuit the short-circuit control element when a first signalvoltage of the first signal is the first voltage and to open theshort-circuit control element when the first signal voltage of the firstsignal is a fourth voltage higher than the first voltage, wherein thesignal generation circuit generates the first signal such that the firstsignal voltage of the first signal is shifted from the first voltage tothe fourth voltage at a first timing corresponding to a rise of theinput signal and that the first signal voltage of the first signal isshifted from the fourth voltage to the first voltage at a fourth timingat which a predetermined time period has passed from a third timingcorresponding to a fall of the input signal, and the signal generationcircuit generates the second signal such that a second signal voltage ofthe second signal is shifted from the first voltage to a fifth voltagehigher than the first voltage at a second timing at which apredetermined time period has passed from the first timing and that thesecond signal voltage of the second signal is shifted from the fifthvoltage to the first voltage at the third timing.
 9. The transmissiondriver according to claim 8, wherein a time period from the first timingto the second timing is equal to or smaller than half a time period fromthe first timing to the third timing, and a time period from the thirdtiming to the fourth timing is equal to or smaller than half a timeperiod from the second timing to the fourth timing.
 10. The transmissiondriver according to claim 9, wherein the fourth voltage and the fifthvoltage are equal to the second voltage.
 11. The transmission driveraccording to claim 4, wherein capacitance of the capacitive element isequal to or greater than ten times parasitic capacitance connected tothe output terminal.
 12. The transmission driver according to claim 1,wherein the circuitry, in operation, operates in: a third mode oftransmitting the transmission signal with a third voltage range thatranges from the first voltage to a sixth voltage higher than the thirdvoltage.
 13. The transmission driver according to claim 12, furthercomprising: a first booster circuit which, in operation, supplies thethird voltage or the sixth voltage.
 14. The transmission driveraccording to claim 13, further comprising: a second booster circuitwhich, in operation, supplies, to the first booster circuit, a seventhpotential voltage higher than the first voltage by a difference betweenthe third voltage and the second voltage or an eighth voltage higherthan the seventh voltage by a difference between the sixth voltage andthe second voltage.
 15. The transmission driver according to claim 14,wherein: the first booster circuit includes a first capacitive elementthat supplies the third voltage or the sixth voltage from a first end ofthe first capacitive element, the second booster circuit includes asecond capacitive element that supplies the seventh voltage or theeighth voltage from a first end of the second capacitive element to thefirst booster circuit, and a first capacitance of the first capacitiveelement is 0.6 times a total of the first capacitance of the firstcapacitive element and a second capacitance of the second capacitiveelement.
 16. The transmission driver according to claim 1, wherein thecircuitry, in operation, operates in: a fourth mode of transmitting thetransmission signal with a fourth voltage range that ranges from thefirst voltage to a ninth voltage that is between the first voltage andthe second voltage; and a fifth mode of transmitting the transmissionsignal with a fifth voltage range that ranges from the first voltage toa tenth voltage that is between the second voltage and the thirdvoltage.
 17. The transmission driver according to claim 16, furthercomprising: a third booster circuit which, in operation, supplies theninth voltage, the tenth voltage, or the third voltage.
 18. Thetransmission driver according to claim 17, wherein: the third boostercircuit divides the first voltage and the second voltage to generate theninth voltage and boosts the ninth voltage that is generated by anamount of the second voltage to generate the tenth voltage.
 19. Anelectronic device comprising: first electrodes that transmit and receivesignals; and a transmission driver which, in operation, receives aninput signal, a first voltage, and a second voltage higher than thefirst voltage, generates a transmission signal according to the inputsignal, and transmits the transmission signal to a corresponding one ofthe first electrodes, wherein the transmission driver, in operation,operates in a first mode of transmitting the transmission signal with afirst voltage range that ranges from the first voltage to the secondvoltage and a second mode of transmitting the transmission signal with asecond voltage range that ranges from the first voltage to a thirdvoltage higher than the second voltage.
 20. The electronic deviceaccording to claim 19, wherein: the transmission driver is mounted on astylus, the first electrodes are mounted on the stylus and transmit andreceive the signals through capacitive coupling between the firstelectrodes and second electrodes mounted on a sensor that is connectedto a sensor controller.
 21. A control method of an electronic devicethat operates in a first mode and a second mode, the electronic deviceincluding electrodes that transmit and receive signals and atransmission driver that receives an input signal, a first voltage, anda second voltage higher than the first voltage and that transmits atransmission signal to the electrodes according to the input signal, thecontrol method comprising: in the first mode, transmitting thetransmission signal with a first voltage range that ranges from thefirst voltage to the second voltage; and in the second mode,transmitting the transmission signal with a second voltage range thatranges from the first voltage to third voltage higher than the secondvoltage.